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1751 lines
77 KiB
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1751 lines
77 KiB
Markdown
---
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title: Rule-based matching
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teaser: Find phrases and tokens, and match entities
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menu:
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- ['Token Matcher', 'matcher']
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- ['Phrase Matcher', 'phrasematcher']
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- ['Dependency Matcher', 'dependencymatcher']
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- ['Entity Ruler', 'entityruler']
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- ['Models & Rules', 'models-rules']
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---
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Compared to using regular expressions on raw text, spaCy's rule-based matcher
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engines and components not only let you find the words and phrases you're
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looking for – they also give you access to the tokens within the document and
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their relationships. This means you can easily access and analyze the
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surrounding tokens, merge spans into single tokens or add entries to the named
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entities in `doc.ents`.
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<Accordion title="Should I use rules or train a model?" id="rules-vs-model">
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For complex tasks, it's usually better to train a statistical entity recognition
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model. However, statistical models require training data, so for many
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situations, rule-based approaches are more practical. This is especially true at
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the start of a project: you can use a rule-based approach as part of a data
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collection process, to help you "bootstrap" a statistical model.
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Training a model is useful if you have some examples and you want your system to
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be able to **generalize** based on those examples. It works especially well if
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there are clues in the _local context_. For instance, if you're trying to detect
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person or company names, your application may benefit from a statistical named
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entity recognition model.
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Rule-based systems are a good choice if there's a more or less **finite number**
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of examples that you want to find in the data, or if there's a very **clear,
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structured pattern** you can express with token rules or regular expressions.
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For instance, country names, IP addresses or URLs are things you might be able
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to handle well with a purely rule-based approach.
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You can also combine both approaches and improve a statistical model with rules
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to handle very specific cases and boost accuracy. For details, see the section
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on [rule-based entity recognition](#entityruler).
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</Accordion>
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<Accordion title="When should I use the token matcher vs. the phrase matcher?" id="matcher-vs-phrase-matcher">
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The `PhraseMatcher` is useful if you already have a large terminology list or
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gazetteer consisting of single or multi-token phrases that you want to find
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exact instances of in your data. As of spaCy v2.1.0, you can also match on the
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`LOWER` attribute for fast and case-insensitive matching.
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The `Matcher` isn't as blazing fast as the `PhraseMatcher`, since it compares
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across individual token attributes. However, it allows you to write very
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abstract representations of the tokens you're looking for, using lexical
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attributes, linguistic features predicted by the model, operators, set
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membership and rich comparison. For example, you can find a noun, followed by a
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verb with the lemma "love" or "like", followed by an optional determiner and
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another token that's at least 10 characters long.
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</Accordion>
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## Token-based matching {#matcher}
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spaCy features a rule-matching engine, the [`Matcher`](/api/matcher), that
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operates over tokens, similar to regular expressions. The rules can refer to
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token annotations (e.g. the token `text` or `tag_`, and flags like `IS_PUNCT`).
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The rule matcher also lets you pass in a custom callback to act on matches – for
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example, to merge entities and apply custom labels. You can also associate
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patterns with entity IDs, to allow some basic entity linking or disambiguation.
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To match large terminology lists, you can use the
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[`PhraseMatcher`](/api/phrasematcher), which accepts `Doc` objects as match
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patterns.
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### Adding patterns {#adding-patterns}
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Let's say we want to enable spaCy to find a combination of three tokens:
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1. A token whose **lowercase form matches "hello"**, e.g. "Hello" or "HELLO".
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2. A token whose **`is_punct` flag is set to `True`**, i.e. any punctuation.
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3. A token whose **lowercase form matches "world"**, e.g. "World" or "WORLD".
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```python
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[{"LOWER": "hello"}, {"IS_PUNCT": True}, {"LOWER": "world"}]
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```
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<Infobox title="Important note" variant="danger">
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When writing patterns, keep in mind that **each dictionary** represents **one
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token**. If spaCy's tokenization doesn't match the tokens defined in a pattern,
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the pattern is not going to produce any results. When developing complex
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patterns, make sure to check examples against spaCy's tokenization:
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```python
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doc = nlp("A complex-example,!")
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print([token.text for token in doc])
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```
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</Infobox>
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First, we initialize the `Matcher` with a vocab. The matcher must always share
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the same vocab with the documents it will operate on. We can now call
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[`matcher.add()`](/api/matcher#add) with an ID and a list of patterns.
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```python
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### {executable="true"}
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import spacy
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from spacy.matcher import Matcher
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nlp = spacy.load("en_core_web_sm")
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matcher = Matcher(nlp.vocab)
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# Add match ID "HelloWorld" with no callback and one pattern
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pattern = [{"LOWER": "hello"}, {"IS_PUNCT": True}, {"LOWER": "world"}]
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matcher.add("HelloWorld", [pattern])
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doc = nlp("Hello, world! Hello world!")
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matches = matcher(doc)
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for match_id, start, end in matches:
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string_id = nlp.vocab.strings[match_id] # Get string representation
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span = doc[start:end] # The matched span
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print(match_id, string_id, start, end, span.text)
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```
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The matcher returns a list of `(match_id, start, end)` tuples – in this case,
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`[('15578876784678163569', 0, 3)]`, which maps to the span `doc[0:3]` of our
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original document. The `match_id` is the [hash value](/usage/spacy-101#vocab) of
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the string ID "HelloWorld". To get the string value, you can look up the ID in
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the [`StringStore`](/api/stringstore).
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```python
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for match_id, start, end in matches:
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string_id = nlp.vocab.strings[match_id] # 'HelloWorld'
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span = doc[start:end] # The matched span
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```
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Optionally, we could also choose to add more than one pattern, for example to
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also match sequences without punctuation between "hello" and "world":
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```python
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patterns = [
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[{"LOWER": "hello"}, {"IS_PUNCT": True}, {"LOWER": "world"}],
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[{"LOWER": "hello"}, {"LOWER": "world"}]
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]
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matcher.add("HelloWorld", patterns)
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```
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By default, the matcher will only return the matches and **not do anything
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else**, like merge entities or assign labels. This is all up to you and can be
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defined individually for each pattern, by passing in a callback function as the
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`on_match` argument on `add()`. This is useful, because it lets you write
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entirely custom and **pattern-specific logic**. For example, you might want to
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merge _some_ patterns into one token, while adding entity labels for other
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pattern types. You shouldn't have to create different matchers for each of those
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processes.
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#### Available token attributes {#adding-patterns-attributes}
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The available token pattern keys correspond to a number of
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[`Token` attributes](/api/token#attributes). The supported attributes for
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rule-based matching are:
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| Attribute | Description |
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| ----------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| `ORTH` | The exact verbatim text of a token. ~~str~~ |
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| `TEXT` <Tag variant="new">2.1</Tag> | The exact verbatim text of a token. ~~str~~ |
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| `NORM` | The normalized form of the token text. ~~str~~ |
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| `LOWER` | The lowercase form of the token text. ~~str~~ |
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| `LENGTH` | The length of the token text. ~~int~~ |
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| `IS_ALPHA`, `IS_ASCII`, `IS_DIGIT` | Token text consists of alphabetic characters, ASCII characters, digits. ~~bool~~ |
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| `IS_LOWER`, `IS_UPPER`, `IS_TITLE` | Token text is in lowercase, uppercase, titlecase. ~~bool~~ |
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| `IS_PUNCT`, `IS_SPACE`, `IS_STOP` | Token is punctuation, whitespace, stop word. ~~bool~~ |
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| `IS_SENT_START` | Token is start of sentence. ~~bool~~ |
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| `LIKE_NUM`, `LIKE_URL`, `LIKE_EMAIL` | Token text resembles a number, URL, email. ~~bool~~ |
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| `SPACY` | Token has a trailing space. ~~bool~~ |
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| `POS`, `TAG`, `MORPH`, `DEP`, `LEMMA`, `SHAPE` | The token's simple and extended part-of-speech tag, morphological analysis, dependency label, lemma, shape. Note that the values of these attributes are case-sensitive. For a list of available part-of-speech tags and dependency labels, see the [Annotation Specifications](/api/annotation). ~~str~~ |
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| `ENT_TYPE` | The token's entity label. ~~str~~ |
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| `_` <Tag variant="new">2.1</Tag> | Properties in [custom extension attributes](/usage/processing-pipelines#custom-components-attributes). ~~Dict[str, Any]~~ |
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| `OP` | [Operator or quantifier](#quantifiers) to determine how often to match a token pattern. ~~str~~ |
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<Accordion title="Does it matter if the attribute names are uppercase or lowercase?">
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No, it shouldn't. spaCy will normalize the names internally and
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`{"LOWER": "text"}` and `{"lower": "text"}` will both produce the same result.
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Using the uppercase version is mostly a convention to make it clear that the
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attributes are "special" and don't exactly map to the token attributes like
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`Token.lower` and `Token.lower_`.
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</Accordion>
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<Accordion title="Why are not all token attributes supported?">
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spaCy can't provide access to all of the attributes because the `Matcher` loops
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over the Cython data, not the Python objects. Inside the matcher, we're dealing
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with a [`TokenC` struct](/api/cython-structs#tokenc) – we don't have an instance
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of [`Token`](/api/token). This means that all of the attributes that refer to
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computed properties can't be accessed.
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The uppercase attribute names like `LOWER` or `IS_PUNCT` refer to symbols from
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the [`spacy.attrs`](%%GITHUB_SPACY/spacy/attrs.pyx) enum table. They're passed
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into a function that essentially is a big case/switch statement, to figure out
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which struct field to return. The same attribute identifiers are used in
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[`Doc.to_array`](/api/doc#to_array), and a few other places in the code where
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you need to describe fields like this.
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</Accordion>
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---
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<Infobox title="Tip: Try the interactive matcher explorer">
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[](https://explosion.ai/demos/matcher)
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The [Matcher Explorer](https://explosion.ai/demos/matcher) lets you test the
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rule-based `Matcher` by creating token patterns interactively and running them
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over your text. Each token can set multiple attributes like text value,
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part-of-speech tag or boolean flags. The token-based view lets you explore how
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spaCy processes your text – and why your pattern matches, or why it doesn't.
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</Infobox>
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#### Extended pattern syntax and attributes {#adding-patterns-attributes-extended new="2.1"}
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Instead of mapping to a single value, token patterns can also map to a
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**dictionary of properties**. For example, to specify that the value of a lemma
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should be part of a list of values, or to set a minimum character length. The
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following rich comparison attributes are available:
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> #### Example
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>
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> ```python
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> # Matches "love cats" or "likes flowers"
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> pattern1 = [{"LEMMA": {"IN": ["like", "love"]}},
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> {"POS": "NOUN"}]
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>
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> # Matches tokens of length >= 10
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> pattern2 = [{"LENGTH": {">=": 10}}]
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>
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> # Match based on morph attributes
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> pattern3 = [{"MORPH": {"IS_SUBSET": ["Number=Sing", "Gender=Neut"]}}]
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> # "", "Number=Sing" and "Number=Sing|Gender=Neut" will match as subsets
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> # "Number=Plur|Gender=Neut" will not match
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> # "Number=Sing|Gender=Neut|Polite=Infm" will not match because it's a superset
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> ```
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| Attribute | Description |
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| -------------------------- | --------------------------------------------------------------------------------------------------------- |
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| `IN` | Attribute value is member of a list. ~~Any~~ |
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| `NOT_IN` | Attribute value is _not_ member of a list. ~~Any~~ |
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| `IS_SUBSET` | Attribute value (for `MORPH` or custom list attributes) is a subset of a list. ~~Any~~ |
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| `IS_SUPERSET` | Attribute value (for `MORPH` or custom list attributes) is a superset of a list. ~~Any~~ |
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| `INTERSECTS` | Attribute value (for `MORPH` or custom list attributes) has a non-empty intersection with a list. ~~Any~~ |
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| `==`, `>=`, `<=`, `>`, `<` | Attribute value is equal, greater or equal, smaller or equal, greater or smaller. ~~Union[int, float]~~ |
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#### Regular expressions {#regex new="2.1"}
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In some cases, only matching tokens and token attributes isn't enough – for
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example, you might want to match different spellings of a word, without having
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to add a new pattern for each spelling.
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```python
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pattern = [{"TEXT": {"REGEX": "^[Uu](\\.?|nited)$"}},
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{"TEXT": {"REGEX": "^[Ss](\\.?|tates)$"}},
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{"LOWER": "president"}]
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```
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The `REGEX` operator allows defining rules for any attribute string value,
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including custom attributes. It always needs to be applied to an attribute like
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`TEXT`, `LOWER` or `TAG`:
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```python
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# Match different spellings of token texts
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pattern = [{"TEXT": {"REGEX": "deff?in[ia]tely"}}]
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# Match tokens with fine-grained POS tags starting with 'V'
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pattern = [{"TAG": {"REGEX": "^V"}}]
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# Match custom attribute values with regular expressions
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pattern = [{"_": {"country": {"REGEX": "^[Uu](nited|\\.?) ?[Ss](tates|\\.?)$"}}}]
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```
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<Infobox title="Important note" variant="warning">
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When using the `REGEX` operator, keep in mind that it operates on **single
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tokens**, not the whole text. Each expression you provide will be matched on a
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token. If you need to match on the whole text instead, see the details on
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[regex matching on the whole text](#regex-text).
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</Infobox>
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##### Matching regular expressions on the full text {#regex-text}
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If your expressions apply to multiple tokens, a simple solution is to match on
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the `doc.text` with `re.finditer` and use the
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[`Doc.char_span`](/api/doc#char_span) method to create a `Span` from the
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character indices of the match. If the matched characters don't map to one or
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more valid tokens, `Doc.char_span` returns `None`.
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> #### What's a valid token sequence?
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>
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> In the example, the expression will also match `"US"` in `"USA"`. However,
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> `"USA"` is a single token and `Span` objects are **sequences of tokens**. So
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> `"US"` cannot be its own span, because it does not end on a token boundary.
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```python
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### {executable="true"}
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import spacy
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import re
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nlp = spacy.load("en_core_web_sm")
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doc = nlp("The United States of America (USA) are commonly known as the United States (U.S. or US) or America.")
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expression = r"[Uu](nited|\\.?) ?[Ss](tates|\\.?)"
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for match in re.finditer(expression, doc.text):
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start, end = match.span()
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span = doc.char_span(start, end)
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# This is a Span object or None if match doesn't map to valid token sequence
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if span is not None:
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print("Found match:", span.text)
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```
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<Accordion title="How can I expand the match to a valid token sequence?">
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In some cases, you might want to expand the match to the closest token
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boundaries, so you can create a `Span` for `"USA"`, even though only the
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substring `"US"` is matched. You can calculate this using the character offsets
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of the tokens in the document, available as
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[`Token.idx`](/api/token#attributes). This lets you create a list of valid token
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start and end boundaries and leaves you with a rather basic algorithmic problem:
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Given a number, find the next lowest (start token) or the next highest (end
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token) number that's part of a given list of numbers. This will be the closest
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valid token boundary.
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There are many ways to do this and the most straightforward one is to create a
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dict keyed by characters in the `Doc`, mapped to the token they're part of. It's
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easy to write and less error-prone, and gives you a constant lookup time: you
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only ever need to create the dict once per `Doc`.
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```python
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chars_to_tokens = {}
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for token in doc:
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for i in range(token.idx, token.idx + len(token.text)):
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chars_to_tokens[i] = token.i
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```
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You can then look up character at a given position, and get the index of the
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corresponding token that the character is part of. Your span would then be
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`doc[token_start:token_end]`. If a character isn't in the dict, it means it's
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the (white)space tokens are split on. That hopefully shouldn't happen, though,
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because it'd mean your regex is producing matches with leading or trailing
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whitespace.
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```python
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### {highlight="5-8"}
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span = doc.char_span(start, end)
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if span is not None:
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print("Found match:", span.text)
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else:
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start_token = chars_to_tokens.get(start)
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end_token = chars_to_tokens.get(end)
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if start_token is not None and end_token is not None:
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span = doc[start_token:end_token + 1]
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print("Found closest match:", span.text)
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```
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</Accordion>
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---
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#### Operators and quantifiers {#quantifiers}
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The matcher also lets you use quantifiers, specified as the `'OP'` key.
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Quantifiers let you define sequences of tokens to be matched, e.g. one or more
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punctuation marks, or specify optional tokens. Note that there are no nested or
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scoped quantifiers – instead, you can build those behaviors with `on_match`
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callbacks.
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||
|
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| OP | Description |
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| --- | ---------------------------------------------------------------- |
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| `!` | Negate the pattern, by requiring it to match exactly 0 times. |
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| `?` | Make the pattern optional, by allowing it to match 0 or 1 times. |
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| `+` | Require the pattern to match 1 or more times. |
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| `*` | Allow the pattern to match zero or more times. |
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> #### Example
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>
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> ```python
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> pattern = [{"LOWER": "hello"},
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> {"IS_PUNCT": True, "OP": "?"}]
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> ```
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||
|
||
<Infobox title="Note on operator behaviour" variant="warning">
|
||
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||
In versions before v2.1.0, the semantics of the `+` and `*` operators behave
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||
inconsistently. They were usually interpreted "greedily", i.e. longer matches
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are returned where possible. However, if you specify two `+` and `*` patterns in
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a row and their matches overlap, the first operator will behave non-greedily.
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This quirk in the semantics is corrected in spaCy v2.1.0.
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</Infobox>
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||
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#### Using wildcard token patterns {#adding-patterns-wildcard new="2"}
|
||
|
||
While the token attributes offer many options to write highly specific patterns,
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||
you can also use an empty dictionary, `{}` as a wildcard representing **any
|
||
token**. This is useful if you know the context of what you're trying to match,
|
||
but very little about the specific token and its characters. For example, let's
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||
say you're trying to extract people's user names from your data. All you know is
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||
that they are listed as "User name: {username}". The name itself may contain any
|
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character, but no whitespace – so you'll know it will be handled as one token.
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||
|
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```python
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[{"ORTH": "User"}, {"ORTH": "name"}, {"ORTH": ":"}, {}]
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```
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||
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#### Validating and debugging patterns {#pattern-validation new="2.1"}
|
||
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The `Matcher` can validate patterns against a JSON schema with the option
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`validate=True`. This is useful for debugging patterns during development, in
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||
particular for catching unsupported attributes.
|
||
|
||
```python
|
||
### {executable="true"}
|
||
import spacy
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||
from spacy.matcher import Matcher
|
||
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||
nlp = spacy.load("en_core_web_sm")
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||
matcher = Matcher(nlp.vocab, validate=True)
|
||
# Add match ID "HelloWorld" with unsupported attribute CASEINSENSITIVE
|
||
pattern = [{"LOWER": "hello"}, {"IS_PUNCT": True}, {"CASEINSENSITIVE": "world"}]
|
||
matcher.add("HelloWorld", [pattern])
|
||
# 🚨 Raises an error:
|
||
# MatchPatternError: Invalid token patterns for matcher rule 'HelloWorld'
|
||
# Pattern 0:
|
||
# - [pattern -> 2 -> CASEINSENSITIVE] extra fields not permitted
|
||
|
||
```
|
||
|
||
### Adding on_match rules {#on_match}
|
||
|
||
To move on to a more realistic example, let's say you're working with a large
|
||
corpus of blog articles, and you want to match all mentions of "Google I/O"
|
||
(which spaCy tokenizes as `['Google', 'I', '/', 'O'`]). To be safe, you only
|
||
match on the uppercase versions, avoiding matches with phrases such as "Google
|
||
i/o".
|
||
|
||
```python
|
||
### {executable="true"}
|
||
from spacy.lang.en import English
|
||
from spacy.matcher import Matcher
|
||
from spacy.tokens import Span
|
||
|
||
nlp = English()
|
||
matcher = Matcher(nlp.vocab)
|
||
|
||
def add_event_ent(matcher, doc, i, matches):
|
||
# Get the current match and create tuple of entity label, start and end.
|
||
# Append entity to the doc's entity. (Don't overwrite doc.ents!)
|
||
match_id, start, end = matches[i]
|
||
entity = Span(doc, start, end, label="EVENT")
|
||
doc.ents += (entity,)
|
||
print(entity.text)
|
||
|
||
pattern = [{"ORTH": "Google"}, {"ORTH": "I"}, {"ORTH": "/"}, {"ORTH": "O"}]
|
||
matcher.add("GoogleIO", [pattern], on_match=add_event_ent)
|
||
doc = nlp("This is a text about Google I/O")
|
||
matches = matcher(doc)
|
||
```
|
||
|
||
A very similar logic has been implemented in the built-in
|
||
[`EntityRuler`](/api/entityruler) by the way. It also takes care of handling
|
||
overlapping matches, which you would otherwise have to take care of yourself.
|
||
|
||
> #### Tip: Visualizing matches
|
||
>
|
||
> When working with entities, you can use [displaCy](/api/top-level#displacy) to
|
||
> quickly generate a NER visualization from your updated `Doc`, which can be
|
||
> exported as an HTML file:
|
||
>
|
||
> ```python
|
||
> from spacy import displacy
|
||
> html = displacy.render(doc, style="ent", page=True,
|
||
> options={"ents": ["EVENT"]})
|
||
> ```
|
||
>
|
||
> For more info and examples, see the usage guide on
|
||
> [visualizing spaCy](/usage/visualizers).
|
||
|
||
We can now call the matcher on our documents. The patterns will be matched in
|
||
the order they occur in the text. The matcher will then iterate over the
|
||
matches, look up the callback for the match ID that was matched, and invoke it.
|
||
|
||
```python
|
||
doc = nlp(YOUR_TEXT_HERE)
|
||
matcher(doc)
|
||
```
|
||
|
||
When the callback is invoked, it is passed four arguments: the matcher itself,
|
||
the document, the position of the current match, and the total list of matches.
|
||
This allows you to write callbacks that consider the entire set of matched
|
||
phrases, so that you can resolve overlaps and other conflicts in whatever way
|
||
you prefer.
|
||
|
||
| Argument | Description |
|
||
| --------- | ------------------------------------------------------------------------------------------------------------------------------------------------- |
|
||
| `matcher` | The matcher instance. ~~Matcher~~ |
|
||
| `doc` | The document the matcher was used on. ~~Doc~~ |
|
||
| `i` | Index of the current match (`matches[i`]). ~~int~~ |
|
||
| `matches` | A list of `(match_id, start, end)` tuples, describing the matches. A match tuple describes a span `doc[start:end`]. ~~List[Tuple[int, int int]]~~ |
|
||
|
||
### Creating spans from matches {#matcher-spans}
|
||
|
||
Creating [`Span`](/api/span) objects from the returned matches is a very common
|
||
use case. spaCy makes this easy by giving you access to the `start` and `end`
|
||
token of each match, which you can use to construct a new span with an optional
|
||
label. As of spaCy v3.0, you can also set `as_spans=True` when calling the
|
||
matcher on a `Doc`, which will return a list of [`Span`](/api/span) objects
|
||
using the `match_id` as the span label.
|
||
|
||
```python
|
||
### {executable="true"}
|
||
import spacy
|
||
from spacy.matcher import Matcher
|
||
from spacy.tokens import Span
|
||
|
||
nlp = spacy.blank("en")
|
||
matcher = Matcher(nlp.vocab)
|
||
matcher.add("PERSON", [[{"lower": "barack"}, {"lower": "obama"}]])
|
||
doc = nlp("Barack Obama was the 44th president of the United States")
|
||
|
||
# 1. Return (match_id, start, end) tuples
|
||
matches = matcher(doc)
|
||
for match_id, start, end in matches:
|
||
# Create the matched span and assign the match_id as a label
|
||
span = Span(doc, start, end, label=match_id)
|
||
print(span.text, span.label_)
|
||
|
||
# 2. Return Span objects directly
|
||
matches = matcher(doc, as_spans=True)
|
||
for span in matches:
|
||
print(span.text, span.label_)
|
||
```
|
||
|
||
### Using custom pipeline components {#matcher-pipeline}
|
||
|
||
Let's say your data also contains some annoying pre-processing artifacts, like
|
||
leftover HTML line breaks (e.g. `<br>` or `<BR/>`). To make your text easier to
|
||
analyze, you want to merge those into one token and flag them, to make sure you
|
||
can ignore them later. Ideally, this should all be done automatically as you
|
||
process the text. You can achieve this by adding a
|
||
[custom pipeline component](/usage/processing-pipelines#custom-components)
|
||
that's called on each `Doc` object, merges the leftover HTML spans and sets an
|
||
attribute `bad_html` on the token.
|
||
|
||
```python
|
||
### {executable="true"}
|
||
import spacy
|
||
from spacy.language import Language
|
||
from spacy.matcher import Matcher
|
||
from spacy.tokens import Token
|
||
|
||
# We're using a component factory because the component needs to be
|
||
# initialized with the shared vocab via the nlp object
|
||
@Language.factory("html_merger")
|
||
def create_bad_html_merger(nlp, name):
|
||
return BadHTMLMerger(nlp.vocab)
|
||
|
||
class BadHTMLMerger:
|
||
def __init__(self, vocab):
|
||
patterns = [
|
||
[{"ORTH": "<"}, {"LOWER": "br"}, {"ORTH": ">"}],
|
||
[{"ORTH": "<"}, {"LOWER": "br/"}, {"ORTH": ">"}],
|
||
]
|
||
# Register a new token extension to flag bad HTML
|
||
Token.set_extension("bad_html", default=False)
|
||
self.matcher = Matcher(vocab)
|
||
self.matcher.add("BAD_HTML", patterns)
|
||
|
||
def __call__(self, doc):
|
||
# This method is invoked when the component is called on a Doc
|
||
matches = self.matcher(doc)
|
||
spans = [] # Collect the matched spans here
|
||
for match_id, start, end in matches:
|
||
spans.append(doc[start:end])
|
||
with doc.retokenize() as retokenizer:
|
||
for span in spans:
|
||
retokenizer.merge(span)
|
||
for token in span:
|
||
token._.bad_html = True # Mark token as bad HTML
|
||
return doc
|
||
|
||
nlp = spacy.load("en_core_web_sm")
|
||
nlp.add_pipe("html_merger", last=True) # Add component to the pipeline
|
||
doc = nlp("Hello<br>world! <br/> This is a test.")
|
||
for token in doc:
|
||
print(token.text, token._.bad_html)
|
||
|
||
```
|
||
|
||
Instead of hard-coding the patterns into the component, you could also make it
|
||
take a path to a JSON file containing the patterns. This lets you reuse the
|
||
component with different patterns, depending on your application. When adding
|
||
the component to the pipeline with [`nlp.add_pipe`](/api/language#add_pipe), you
|
||
can pass in the argument via the `config`:
|
||
|
||
```python
|
||
@Language.factory("html_merger", default_config={"path": None})
|
||
def create_bad_html_merger(nlp, name, path):
|
||
return BadHTMLMerger(nlp, path=path)
|
||
|
||
nlp.add_pipe("html_merger", config={"path": "/path/to/patterns.json"})
|
||
```
|
||
|
||
<Infobox title="Processing pipelines" emoji="📖">
|
||
|
||
For more details and examples of how to **create custom pipeline components**
|
||
and **extension attributes**, see the
|
||
[usage guide](/usage/processing-pipelines).
|
||
|
||
</Infobox>
|
||
|
||
### Example: Using linguistic annotations {#example1}
|
||
|
||
Let's say you're analyzing user comments and you want to find out what people
|
||
are saying about Facebook. You want to start off by finding adjectives following
|
||
"Facebook is" or "Facebook was". This is obviously a very rudimentary solution,
|
||
but it'll be fast, and a great way to get an idea for what's in your data. Your
|
||
pattern could look like this:
|
||
|
||
```python
|
||
[{"LOWER": "facebook"}, {"LEMMA": "be"}, {"POS": "ADV", "OP": "*"}, {"POS": "ADJ"}]
|
||
```
|
||
|
||
This translates to a token whose lowercase form matches "facebook" (like
|
||
Facebook, facebook or FACEBOOK), followed by a token with the lemma "be" (for
|
||
example, is, was, or 's), followed by an **optional** adverb, followed by an
|
||
adjective. Using the linguistic annotations here is especially useful, because
|
||
you can tell spaCy to match "Facebook's annoying", but **not** "Facebook's
|
||
annoying ads". The optional adverb makes sure you won't miss adjectives with
|
||
intensifiers, like "pretty awful" or "very nice".
|
||
|
||
To get a quick overview of the results, you could collect all sentences
|
||
containing a match and render them with the
|
||
[displaCy visualizer](/usage/visualizers). In the callback function, you'll have
|
||
access to the `start` and `end` of each match, as well as the parent `Doc`. This
|
||
lets you determine the sentence containing the match, `doc[start:end].sent`, and
|
||
calculate the start and end of the matched span within the sentence. Using
|
||
displaCy in ["manual" mode](/usage/visualizers#manual-usage) lets you pass in a
|
||
list of dictionaries containing the text and entities to render.
|
||
|
||
```python
|
||
### {executable="true"}
|
||
import spacy
|
||
from spacy import displacy
|
||
from spacy.matcher import Matcher
|
||
|
||
nlp = spacy.load("en_core_web_sm")
|
||
matcher = Matcher(nlp.vocab)
|
||
matched_sents = [] # Collect data of matched sentences to be visualized
|
||
|
||
def collect_sents(matcher, doc, i, matches):
|
||
match_id, start, end = matches[i]
|
||
span = doc[start:end] # Matched span
|
||
sent = span.sent # Sentence containing matched span
|
||
# Append mock entity for match in displaCy style to matched_sents
|
||
# get the match span by ofsetting the start and end of the span with the
|
||
# start and end of the sentence in the doc
|
||
match_ents = [{
|
||
"start": span.start_char - sent.start_char,
|
||
"end": span.end_char - sent.start_char,
|
||
"label": "MATCH",
|
||
}]
|
||
matched_sents.append({"text": sent.text, "ents": match_ents})
|
||
|
||
pattern = [{"LOWER": "facebook"}, {"LEMMA": "be"}, {"POS": "ADV", "OP": "*"},
|
||
{"POS": "ADJ"}]
|
||
matcher.add("FacebookIs", [pattern], on_match=collect_sents) # add pattern
|
||
doc = nlp("I'd say that Facebook is evil. – Facebook is pretty cool, right?")
|
||
matches = matcher(doc)
|
||
|
||
# Serve visualization of sentences containing match with displaCy
|
||
# set manual=True to make displaCy render straight from a dictionary
|
||
# (if you're not running the code within a Jupyer environment, you can
|
||
# use displacy.serve instead)
|
||
displacy.render(matched_sents, style="ent", manual=True)
|
||
```
|
||
|
||
### Example: Phone numbers {#example2}
|
||
|
||
Phone numbers can have many different formats and matching them is often tricky.
|
||
During tokenization, spaCy will leave sequences of numbers intact and only split
|
||
on whitespace and punctuation. This means that your match pattern will have to
|
||
look out for number sequences of a certain length, surrounded by specific
|
||
punctuation – depending on the
|
||
[national conventions](https://en.wikipedia.org/wiki/National_conventions_for_writing_telephone_numbers).
|
||
|
||
The `IS_DIGIT` flag is not very helpful here, because it doesn't tell us
|
||
anything about the length. However, you can use the `SHAPE` flag, with each `d`
|
||
representing a digit (up to 4 digits / characters):
|
||
|
||
```python
|
||
[{"ORTH": "("}, {"SHAPE": "ddd"}, {"ORTH": ")"}, {"SHAPE": "dddd"},
|
||
{"ORTH": "-", "OP": "?"}, {"SHAPE": "dddd"}]
|
||
```
|
||
|
||
This will match phone numbers of the format **(123) 4567 8901** or **(123)
|
||
4567-8901**. To also match formats like **(123) 456 789**, you can add a second
|
||
pattern using `'ddd'` in place of `'dddd'`. By hard-coding some values, you can
|
||
match only certain, country-specific numbers. For example, here's a pattern to
|
||
match the most common formats of
|
||
[international German numbers](https://en.wikipedia.org/wiki/National_conventions_for_writing_telephone_numbers#Germany):
|
||
|
||
```python
|
||
[{"ORTH": "+"}, {"ORTH": "49"}, {"ORTH": "(", "OP": "?"}, {"SHAPE": "dddd"},
|
||
{"ORTH": ")", "OP": "?"}, {"SHAPE": "dddd", "LENGTH": 6}]
|
||
```
|
||
|
||
Depending on the formats your application needs to match, creating an extensive
|
||
set of rules like this is often better than training a model. It'll produce more
|
||
predictable results, is much easier to modify and extend, and doesn't require
|
||
any training data – only a set of test cases.
|
||
|
||
```python
|
||
### {executable="true"}
|
||
import spacy
|
||
from spacy.matcher import Matcher
|
||
|
||
nlp = spacy.load("en_core_web_sm")
|
||
matcher = Matcher(nlp.vocab)
|
||
pattern = [{"ORTH": "("}, {"SHAPE": "ddd"}, {"ORTH": ")"}, {"SHAPE": "ddd"},
|
||
{"ORTH": "-", "OP": "?"}, {"SHAPE": "ddd"}]
|
||
matcher.add("PHONE_NUMBER", [pattern])
|
||
|
||
doc = nlp("Call me at (123) 456 789 or (123) 456 789!")
|
||
print([t.text for t in doc])
|
||
matches = matcher(doc)
|
||
for match_id, start, end in matches:
|
||
span = doc[start:end]
|
||
print(span.text)
|
||
```
|
||
|
||
### Example: Hashtags and emoji on social media {#example3}
|
||
|
||
Social media posts, especially tweets, can be difficult to work with. They're
|
||
very short and often contain various emoji and hashtags. By only looking at the
|
||
plain text, you'll lose a lot of valuable semantic information.
|
||
|
||
Let's say you've extracted a large sample of social media posts on a specific
|
||
topic, for example posts mentioning a brand name or product. As the first step
|
||
of your data exploration, you want to filter out posts containing certain emoji
|
||
and use them to assign a general sentiment score, based on whether the expressed
|
||
emotion is positive or negative, e.g. 😀 or 😞. You also want to find, merge and
|
||
label hashtags like `#MondayMotivation`, to be able to ignore or analyze them
|
||
later.
|
||
|
||
> #### Note on sentiment analysis
|
||
>
|
||
> Ultimately, sentiment analysis is not always _that_ easy. In addition to the
|
||
> emoji, you'll also want to take specific words into account and check the
|
||
> `subtree` for intensifiers like "very", to increase the sentiment score. At
|
||
> some point, you might also want to train a sentiment model. However, the
|
||
> approach described in this example is very useful for **bootstrapping rules to
|
||
> collect training data**. It's also an incredibly fast way to gather first
|
||
> insights into your data – with about 1 million tweets, you'd be looking at a
|
||
> processing time of **under 1 minute**.
|
||
|
||
By default, spaCy's tokenizer will split emoji into separate tokens. This means
|
||
that you can create a pattern for one or more emoji tokens. Valid hashtags
|
||
usually consist of a `#`, plus a sequence of ASCII characters with no
|
||
whitespace, making them easy to match as well.
|
||
|
||
```python
|
||
### {executable="true"}
|
||
from spacy.lang.en import English
|
||
from spacy.matcher import Matcher
|
||
|
||
nlp = English() # We only want the tokenizer, so no need to load a pipeline
|
||
matcher = Matcher(nlp.vocab)
|
||
|
||
pos_emoji = ["😀", "😃", "😂", "🤣", "😊", "😍"] # Positive emoji
|
||
neg_emoji = ["😞", "😠", "😩", "😢", "😭", "😒"] # Negative emoji
|
||
|
||
# Add patterns to match one or more emoji tokens
|
||
pos_patterns = [[{"ORTH": emoji}] for emoji in pos_emoji]
|
||
neg_patterns = [[{"ORTH": emoji}] for emoji in neg_emoji]
|
||
|
||
# Function to label the sentiment
|
||
def label_sentiment(matcher, doc, i, matches):
|
||
match_id, start, end = matches[i]
|
||
if doc.vocab.strings[match_id] == "HAPPY": # Don't forget to get string!
|
||
doc.sentiment += 0.1 # Add 0.1 for positive sentiment
|
||
elif doc.vocab.strings[match_id] == "SAD":
|
||
doc.sentiment -= 0.1 # Subtract 0.1 for negative sentiment
|
||
|
||
matcher.add("HAPPY", pos_patterns, on_match=label_sentiment) # Add positive pattern
|
||
matcher.add("SAD", neg_patterns, on_match=label_sentiment) # Add negative pattern
|
||
|
||
# Add pattern for valid hashtag, i.e. '#' plus any ASCII token
|
||
matcher.add("HASHTAG", [[{"ORTH": "#"}, {"IS_ASCII": True}]])
|
||
|
||
doc = nlp("Hello world 😀 #MondayMotivation")
|
||
matches = matcher(doc)
|
||
for match_id, start, end in matches:
|
||
string_id = doc.vocab.strings[match_id] # Look up string ID
|
||
span = doc[start:end]
|
||
print(string_id, span.text)
|
||
```
|
||
|
||
Because the `on_match` callback receives the ID of each match, you can use the
|
||
same function to handle the sentiment assignment for both the positive and
|
||
negative pattern. To keep it simple, we'll either add or subtract `0.1` points –
|
||
this way, the score will also reflect combinations of emoji, even positive _and_
|
||
negative ones.
|
||
|
||
With a library like [Emojipedia](https://github.com/bcongdon/python-emojipedia),
|
||
we can also retrieve a short description for each emoji – for example, 😍's
|
||
official title is "Smiling Face With Heart-Eyes". Assigning it to a
|
||
[custom attribute](/usage/processing-pipelines#custom-components-attributes) on
|
||
the emoji span will make it available as `span._.emoji_desc`.
|
||
|
||
```python
|
||
from emojipedia import Emojipedia # Installation: pip install emojipedia
|
||
from spacy.tokens import Span # Get the global Span object
|
||
|
||
Span.set_extension("emoji_desc", default=None) # Register the custom attribute
|
||
|
||
def label_sentiment(matcher, doc, i, matches):
|
||
match_id, start, end = matches[i]
|
||
if doc.vocab.strings[match_id] == "HAPPY": # Don't forget to get string!
|
||
doc.sentiment += 0.1 # Add 0.1 for positive sentiment
|
||
elif doc.vocab.strings[match_id] == "SAD":
|
||
doc.sentiment -= 0.1 # Subtract 0.1 for negative sentiment
|
||
span = doc[start:end]
|
||
emoji = Emojipedia.search(span[0].text) # Get data for emoji
|
||
span._.emoji_desc = emoji.title # Assign emoji description
|
||
|
||
```
|
||
|
||
To label the hashtags, we can use a
|
||
[custom attribute](/usage/processing-pipelines#custom-components-attributes) set
|
||
on the respective token:
|
||
|
||
```python
|
||
### {executable="true"}
|
||
import spacy
|
||
from spacy.matcher import Matcher
|
||
from spacy.tokens import Token
|
||
|
||
nlp = spacy.load("en_core_web_sm")
|
||
matcher = Matcher(nlp.vocab)
|
||
|
||
# Add pattern for valid hashtag, i.e. '#' plus any ASCII token
|
||
matcher.add("HASHTAG", [[{"ORTH": "#"}, {"IS_ASCII": True}]])
|
||
|
||
# Register token extension
|
||
Token.set_extension("is_hashtag", default=False)
|
||
|
||
doc = nlp("Hello world 😀 #MondayMotivation")
|
||
matches = matcher(doc)
|
||
hashtags = []
|
||
for match_id, start, end in matches:
|
||
if doc.vocab.strings[match_id] == "HASHTAG":
|
||
hashtags.append(doc[start:end])
|
||
with doc.retokenize() as retokenizer:
|
||
for span in hashtags:
|
||
retokenizer.merge(span)
|
||
for token in span:
|
||
token._.is_hashtag = True
|
||
|
||
for token in doc:
|
||
print(token.text, token._.is_hashtag)
|
||
```
|
||
|
||
## Efficient phrase matching {#phrasematcher}
|
||
|
||
If you need to match large terminology lists, you can also use the
|
||
[`PhraseMatcher`](/api/phrasematcher) and create [`Doc`](/api/doc) objects
|
||
instead of token patterns, which is much more efficient overall. The `Doc`
|
||
patterns can contain single or multiple tokens.
|
||
|
||
### Adding phrase patterns {#adding-phrase-patterns}
|
||
|
||
```python
|
||
### {executable="true"}
|
||
import spacy
|
||
from spacy.matcher import PhraseMatcher
|
||
|
||
nlp = spacy.load("en_core_web_sm")
|
||
matcher = PhraseMatcher(nlp.vocab)
|
||
terms = ["Barack Obama", "Angela Merkel", "Washington, D.C."]
|
||
# Only run nlp.make_doc to speed things up
|
||
patterns = [nlp.make_doc(text) for text in terms]
|
||
matcher.add("TerminologyList", patterns)
|
||
|
||
doc = nlp("German Chancellor Angela Merkel and US President Barack Obama "
|
||
"converse in the Oval Office inside the White House in Washington, D.C.")
|
||
matches = matcher(doc)
|
||
for match_id, start, end in matches:
|
||
span = doc[start:end]
|
||
print(span.text)
|
||
```
|
||
|
||
Since spaCy is used for processing both the patterns and the text to be matched,
|
||
you won't have to worry about specific tokenization – for example, you can
|
||
simply pass in `nlp("Washington, D.C.")` and won't have to write a complex token
|
||
pattern covering the exact tokenization of the term.
|
||
|
||
<Infobox title="Important note on creating patterns" variant="warning">
|
||
|
||
To create the patterns, each phrase has to be processed with the `nlp` object.
|
||
If you have a trained pipeline loaded, doing this in a loop or list
|
||
comprehension can easily become inefficient and slow. If you **only need the
|
||
tokenization and lexical attributes**, you can run
|
||
[`nlp.make_doc`](/api/language#make_doc) instead, which will only run the
|
||
tokenizer. For an additional speed boost, you can also use the
|
||
[`nlp.tokenizer.pipe`](/api/tokenizer#pipe) method, which will process the texts
|
||
as a stream.
|
||
|
||
```diff
|
||
- patterns = [nlp(term) for term in LOTS_OF_TERMS]
|
||
+ patterns = [nlp.make_doc(term) for term in LOTS_OF_TERMS]
|
||
+ patterns = list(nlp.tokenizer.pipe(LOTS_OF_TERMS))
|
||
```
|
||
|
||
</Infobox>
|
||
|
||
### Matching on other token attributes {#phrasematcher-attrs new="2.1"}
|
||
|
||
By default, the `PhraseMatcher` will match on the verbatim token text, e.g.
|
||
`Token.text`. By setting the `attr` argument on initialization, you can change
|
||
**which token attribute the matcher should use** when comparing the phrase
|
||
pattern to the matched `Doc`. For example, using the attribute `LOWER` lets you
|
||
match on `Token.lower` and create case-insensitive match patterns:
|
||
|
||
```python
|
||
### {executable="true"}
|
||
from spacy.lang.en import English
|
||
from spacy.matcher import PhraseMatcher
|
||
|
||
nlp = English()
|
||
matcher = PhraseMatcher(nlp.vocab, attr="LOWER")
|
||
patterns = [nlp.make_doc(name) for name in ["Angela Merkel", "Barack Obama"]]
|
||
matcher.add("Names", patterns)
|
||
|
||
doc = nlp("angela merkel and us president barack Obama")
|
||
for match_id, start, end in matcher(doc):
|
||
print("Matched based on lowercase token text:", doc[start:end])
|
||
```
|
||
|
||
<Infobox title="Important note on creating patterns" variant="warning">
|
||
|
||
The examples here use [`nlp.make_doc`](/api/language#make_doc) to create `Doc`
|
||
object patterns as efficiently as possible and without running any of the other
|
||
pipeline components. If the token attribute you want to match on is set by a
|
||
pipeline component, **make sure that the pipeline component runs** when you
|
||
create the pattern. For example, to match on `POS` or `LEMMA`, the pattern `Doc`
|
||
objects need to have part-of-speech tags set by the `tagger` or `morphologizer`.
|
||
You can either call the `nlp` object on your pattern texts instead of
|
||
`nlp.make_doc`, or use [`nlp.select_pipes`](/api/language#select_pipes) to
|
||
disable components selectively.
|
||
|
||
</Infobox>
|
||
|
||
Another possible use case is matching number tokens like IP addresses based on
|
||
their shape. This means that you won't have to worry about how those strings
|
||
will be tokenized and you'll be able to find tokens and combinations of tokens
|
||
based on a few examples. Here, we're matching on the shapes `ddd.d.d.d` and
|
||
`ddd.ddd.d.d`:
|
||
|
||
```python
|
||
### {executable="true"}
|
||
from spacy.lang.en import English
|
||
from spacy.matcher import PhraseMatcher
|
||
|
||
nlp = English()
|
||
matcher = PhraseMatcher(nlp.vocab, attr="SHAPE")
|
||
matcher.add("IP", [nlp("127.0.0.1"), nlp("127.127.0.0")])
|
||
|
||
doc = nlp("Often the router will have an IP address such as 192.168.1.1 or 192.168.2.1.")
|
||
for match_id, start, end in matcher(doc):
|
||
print("Matched based on token shape:", doc[start:end])
|
||
```
|
||
|
||
In theory, the same also works for attributes like `POS`. For example, a pattern
|
||
`nlp("I like cats")` matched based on its part-of-speech tag would return a
|
||
match for "I love dogs". You could also match on boolean flags like `IS_PUNCT`
|
||
to match phrases with the same sequence of punctuation and non-punctuation
|
||
tokens as the pattern. But this can easily get confusing and doesn't have much
|
||
of an advantage over writing one or two token patterns.
|
||
|
||
## Dependency Matcher {#dependencymatcher new="3" model="parser"}
|
||
|
||
The [`DependencyMatcher`](/api/dependencymatcher) lets you match patterns within
|
||
the dependency parse using
|
||
[Semgrex](https://nlp.stanford.edu/nlp/javadoc/javanlp/edu/stanford/nlp/semgraph/semgrex/SemgrexPattern.html)
|
||
operators. It requires a model containing a parser such as the
|
||
[`DependencyParser`](/api/dependencyparser). Instead of defining a list of
|
||
adjacent tokens as in `Matcher` patterns, the `DependencyMatcher` patterns match
|
||
tokens in the dependency parse and specify the relations between them.
|
||
|
||
> ```python
|
||
> ### Example
|
||
> from spacy.matcher import DependencyMatcher
|
||
>
|
||
> # "[subject] ... initially founded"
|
||
> pattern = [
|
||
> # anchor token: founded
|
||
> {
|
||
> "RIGHT_ID": "founded",
|
||
> "RIGHT_ATTRS": {"ORTH": "founded"}
|
||
> },
|
||
> # founded -> subject
|
||
> {
|
||
> "LEFT_ID": "founded",
|
||
> "REL_OP": ">",
|
||
> "RIGHT_ID": "subject",
|
||
> "RIGHT_ATTRS": {"DEP": "nsubj"}
|
||
> },
|
||
> # "founded" follows "initially"
|
||
> {
|
||
> "LEFT_ID": "founded",
|
||
> "REL_OP": ";",
|
||
> "RIGHT_ID": "initially",
|
||
> "RIGHT_ATTRS": {"ORTH": "initially"}
|
||
> }
|
||
> ]
|
||
>
|
||
> matcher = DependencyMatcher(nlp.vocab)
|
||
> matcher.add("FOUNDED", [pattern])
|
||
> matches = matcher(doc)
|
||
> ```
|
||
|
||
A pattern added to the dependency matcher consists of a **list of
|
||
dictionaries**, with each dictionary describing a **token to match** and its
|
||
**relation to an existing token** in the pattern. Except for the first
|
||
dictionary, which defines an anchor token using only `RIGHT_ID` and
|
||
`RIGHT_ATTRS`, each pattern should have the following keys:
|
||
|
||
| Name | Description |
|
||
| ------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
|
||
| `LEFT_ID` | The name of the left-hand node in the relation, which has been defined in an earlier node. ~~str~~ |
|
||
| `REL_OP` | An operator that describes how the two nodes are related. ~~str~~ |
|
||
| `RIGHT_ID` | A unique name for the right-hand node in the relation. ~~str~~ |
|
||
| `RIGHT_ATTRS` | The token attributes to match for the right-hand node in the same format as patterns provided to the regular token-based [`Matcher`](/api/matcher). ~~Dict[str, Any]~~ |
|
||
|
||
Each additional token added to the pattern is linked to an existing token
|
||
`LEFT_ID` by the relation `REL_OP`. The new token is given the name `RIGHT_ID`
|
||
and described by the attributes `RIGHT_ATTRS`.
|
||
|
||
<Infobox title="Important note" variant="warning">
|
||
|
||
Because the unique token **names** in `LEFT_ID` and `RIGHT_ID` are used to
|
||
identify tokens, the order of the dicts in the patterns is important: a token
|
||
name needs to be defined as `RIGHT_ID` in one dict in the pattern **before** it
|
||
can be used as `LEFT_ID` in another dict.
|
||
|
||
</Infobox>
|
||
|
||
### Dependency matcher operators {#dependencymatcher-operators}
|
||
|
||
The following operators are supported by the `DependencyMatcher`, most of which
|
||
come directly from
|
||
[Semgrex](https://nlp.stanford.edu/nlp/javadoc/javanlp/edu/stanford/nlp/semgraph/semgrex/SemgrexPattern.html):
|
||
|
||
| Symbol | Description |
|
||
| --------- | -------------------------------------------------------------------------------------------------------------------- |
|
||
| `A < B` | `A` is the immediate dependent of `B`. |
|
||
| `A > B` | `A` is the immediate head of `B`. |
|
||
| `A << B` | `A` is the dependent in a chain to `B` following dep → head paths. |
|
||
| `A >> B` | `A` is the head in a chain to `B` following head → dep paths. |
|
||
| `A . B` | `A` immediately precedes `B`, i.e. `A.i == B.i - 1`, and both are within the same dependency tree. |
|
||
| `A .* B` | `A` precedes `B`, i.e. `A.i < B.i`, and both are within the same dependency tree _(not in Semgrex)_. |
|
||
| `A ; B` | `A` immediately follows `B`, i.e. `A.i == B.i + 1`, and both are within the same dependency tree _(not in Semgrex)_. |
|
||
| `A ;* B` | `A` follows `B`, i.e. `A.i > B.i`, and both are within the same dependency tree _(not in Semgrex)_. |
|
||
| `A $+ B` | `B` is a right immediate sibling of `A`, i.e. `A` and `B` have the same parent and `A.i == B.i - 1`. |
|
||
| `A $- B` | `B` is a left immediate sibling of `A`, i.e. `A` and `B` have the same parent and `A.i == B.i + 1`. |
|
||
| `A $++ B` | `B` is a right sibling of `A`, i.e. `A` and `B` have the same parent and `A.i < B.i`. |
|
||
| `A $-- B` | `B` is a left sibling of `A`, i.e. `A` and `B` have the same parent and `A.i > B.i`. |
|
||
|
||
### Designing dependency matcher patterns {#dependencymatcher-patterns}
|
||
|
||
Let's say we want to find sentences describing who founded what kind of company:
|
||
|
||
- _Smith founded a healthcare company in 2005._
|
||
- _Williams initially founded an insurance company in 1987._
|
||
- _Lee, an experienced CEO, has founded two AI startups._
|
||
|
||
The dependency parse for "Smith founded a healthcare company" shows types of
|
||
relations and tokens we want to match:
|
||
|
||
> #### Visualizing the parse
|
||
>
|
||
> The [`displacy` visualizer](/usage/visualizers) lets you render `Doc` objects
|
||
> and their dependency parse and part-of-speech tags:
|
||
>
|
||
> ```python
|
||
> import spacy
|
||
> from spacy import displacy
|
||
>
|
||
> nlp = spacy.load("en_core_web_sm")
|
||
> doc = nlp("Smith founded a healthcare company")
|
||
> displacy.serve(doc)
|
||
> ```
|
||
|
||
import DisplaCyDepFoundedHtml from 'images/displacy-dep-founded.html'
|
||
|
||
<Iframe title="displaCy visualization of dependencies" html={DisplaCyDepFoundedHtml} height={450} />
|
||
|
||
The relations we're interested in are:
|
||
|
||
- the founder is the **subject** (`nsubj`) of the token with the text `founded`
|
||
- the company is the **object** (`dobj`) of `founded`
|
||
- the kind of company may be an **adjective** (`amod`, not shown above) or a
|
||
**compound** (`compound`)
|
||
|
||
The first step is to pick an **anchor token** for the pattern. Since it's the
|
||
root of the dependency parse, `founded` is a good choice here. It is often
|
||
easier to construct patterns when all dependency relation operators point from
|
||
the head to the children. In this example, we'll only use `>`, which connects a
|
||
head to an immediate dependent as `head > child`.
|
||
|
||
The simplest dependency matcher pattern will identify and name a single token in
|
||
the tree:
|
||
|
||
```python
|
||
### {executable="true"}
|
||
import spacy
|
||
from spacy.matcher import DependencyMatcher
|
||
|
||
nlp = spacy.load("en_core_web_sm")
|
||
matcher = DependencyMatcher(nlp.vocab)
|
||
pattern = [
|
||
{
|
||
"RIGHT_ID": "anchor_founded", # unique name
|
||
"RIGHT_ATTRS": {"ORTH": "founded"} # token pattern for "founded"
|
||
}
|
||
]
|
||
matcher.add("FOUNDED", [pattern])
|
||
doc = nlp("Smith founded two companies.")
|
||
matches = matcher(doc)
|
||
print(matches) # [(4851363122962674176, [1])]
|
||
```
|
||
|
||
Now that we have a named anchor token (`anchor_founded`), we can add the founder
|
||
as the immediate dependent (`>`) of `founded` with the dependency label `nsubj`:
|
||
|
||
```python
|
||
### Step 1 {highlight="8,10"}
|
||
pattern = [
|
||
{
|
||
"RIGHT_ID": "anchor_founded",
|
||
"RIGHT_ATTRS": {"ORTH": "founded"}
|
||
},
|
||
{
|
||
"LEFT_ID": "anchor_founded",
|
||
"REL_OP": ">",
|
||
"RIGHT_ID": "founded_subject",
|
||
"RIGHT_ATTRS": {"DEP": "nsubj"},
|
||
}
|
||
# ...
|
||
]
|
||
```
|
||
|
||
The direct object (`dobj`) is added in the same way:
|
||
|
||
```python
|
||
### Step 2 {highlight=""}
|
||
pattern = [
|
||
#...
|
||
{
|
||
"LEFT_ID": "anchor_founded",
|
||
"REL_OP": ">",
|
||
"RIGHT_ID": "founded_object",
|
||
"RIGHT_ATTRS": {"DEP": "dobj"},
|
||
}
|
||
# ...
|
||
]
|
||
```
|
||
|
||
When the subject and object tokens are added, they are required to have names
|
||
under the key `RIGHT_ID`, which are allowed to be any unique string, e.g.
|
||
`founded_subject`. These names can then be used as `LEFT_ID` to **link new
|
||
tokens into the pattern**. For the final part of our pattern, we'll specify that
|
||
the token `founded_object` should have a modifier with the dependency relation
|
||
`amod` or `compound`:
|
||
|
||
```python
|
||
### Step 3 {highlight="7"}
|
||
pattern = [
|
||
# ...
|
||
{
|
||
"LEFT_ID": "founded_object",
|
||
"REL_OP": ">",
|
||
"RIGHT_ID": "founded_object_modifier",
|
||
"RIGHT_ATTRS": {"DEP": {"IN": ["amod", "compound"]}},
|
||
}
|
||
]
|
||
```
|
||
|
||
You can picture the process of creating a dependency matcher pattern as defining
|
||
an anchor token on the left and building up the pattern by linking tokens
|
||
one-by-one on the right using relation operators. To create a valid pattern,
|
||
each new token needs to be linked to an existing token on its left. As for
|
||
`founded` in this example, a token may be linked to more than one token on its
|
||
right:
|
||
|
||
|
||
|
||
The full pattern comes together as shown in the example below:
|
||
|
||
```python
|
||
### {executable="true"}
|
||
import spacy
|
||
from spacy.matcher import DependencyMatcher
|
||
|
||
nlp = spacy.load("en_core_web_sm")
|
||
matcher = DependencyMatcher(nlp.vocab)
|
||
|
||
pattern = [
|
||
{
|
||
"RIGHT_ID": "anchor_founded",
|
||
"RIGHT_ATTRS": {"ORTH": "founded"}
|
||
},
|
||
{
|
||
"LEFT_ID": "anchor_founded",
|
||
"REL_OP": ">",
|
||
"RIGHT_ID": "founded_subject",
|
||
"RIGHT_ATTRS": {"DEP": "nsubj"},
|
||
},
|
||
{
|
||
"LEFT_ID": "anchor_founded",
|
||
"REL_OP": ">",
|
||
"RIGHT_ID": "founded_object",
|
||
"RIGHT_ATTRS": {"DEP": "dobj"},
|
||
},
|
||
{
|
||
"LEFT_ID": "founded_object",
|
||
"REL_OP": ">",
|
||
"RIGHT_ID": "founded_object_modifier",
|
||
"RIGHT_ATTRS": {"DEP": {"IN": ["amod", "compound"]}},
|
||
}
|
||
]
|
||
|
||
matcher.add("FOUNDED", [pattern])
|
||
doc = nlp("Lee, an experienced CEO, has founded two AI startups.")
|
||
matches = matcher(doc)
|
||
|
||
print(matches) # [(4851363122962674176, [6, 0, 10, 9])]
|
||
# Each token_id corresponds to one pattern dict
|
||
match_id, token_ids = matches[0]
|
||
for i in range(len(token_ids)):
|
||
print(pattern[i]["RIGHT_ID"] + ":", doc[token_ids[i]].text)
|
||
```
|
||
|
||
<Infobox title="Important note on speed" variant="warning">
|
||
|
||
The dependency matcher may be slow when token patterns can potentially match
|
||
many tokens in the sentence or when relation operators allow longer paths in the
|
||
dependency parse, e.g. `<<`, `>>`, `.*` and `;*`.
|
||
|
||
To improve the matcher speed, try to make your token patterns and operators as
|
||
specific as possible. For example, use `>` instead of `>>` if possible and use
|
||
token patterns that include dependency labels and other token attributes instead
|
||
of patterns such as `{}` that match any token in the sentence.
|
||
|
||
</Infobox>
|
||
|
||
## Rule-based entity recognition {#entityruler new="2.1"}
|
||
|
||
The [`EntityRuler`](/api/entityruler) is a component that lets you add named
|
||
entities based on pattern dictionaries, which makes it easy to combine
|
||
rule-based and statistical named entity recognition for even more powerful
|
||
pipelines.
|
||
|
||
### Entity Patterns {#entityruler-patterns}
|
||
|
||
Entity patterns are dictionaries with two keys: `"label"`, specifying the label
|
||
to assign to the entity if the pattern is matched, and `"pattern"`, the match
|
||
pattern. The entity ruler accepts two types of patterns:
|
||
|
||
1. **Phrase patterns** for exact string matches (string).
|
||
|
||
```python
|
||
{"label": "ORG", "pattern": "Apple"}
|
||
```
|
||
|
||
2. **Token patterns** with one dictionary describing one token (list).
|
||
|
||
```python
|
||
{"label": "GPE", "pattern": [{"LOWER": "san"}, {"LOWER": "francisco"}]}
|
||
```
|
||
|
||
### Using the entity ruler {#entityruler-usage}
|
||
|
||
The [`EntityRuler`](/api/entityruler) is a pipeline component that's typically
|
||
added via [`nlp.add_pipe`](/api/language#add_pipe). When the `nlp` object is
|
||
called on a text, it will find matches in the `doc` and add them as entities to
|
||
the `doc.ents`, using the specified pattern label as the entity label. If any
|
||
matches were to overlap, the pattern matching most tokens takes priority. If
|
||
they also happen to be equally long, then the match occurring first in the `Doc`
|
||
is chosen.
|
||
|
||
```python
|
||
### {executable="true"}
|
||
from spacy.lang.en import English
|
||
|
||
nlp = English()
|
||
ruler = nlp.add_pipe("entity_ruler")
|
||
patterns = [{"label": "ORG", "pattern": "Apple"},
|
||
{"label": "GPE", "pattern": [{"LOWER": "san"}, {"LOWER": "francisco"}]}]
|
||
ruler.add_patterns(patterns)
|
||
|
||
doc = nlp("Apple is opening its first big office in San Francisco.")
|
||
print([(ent.text, ent.label_) for ent in doc.ents])
|
||
```
|
||
|
||
The entity ruler is designed to integrate with spaCy's existing pipeline
|
||
components and enhance the named entity recognizer. If it's added **before the
|
||
`"ner"` component**, the entity recognizer will respect the existing entity
|
||
spans and adjust its predictions around it. This can significantly improve
|
||
accuracy in some cases. If it's added **after the `"ner"` component**, the
|
||
entity ruler will only add spans to the `doc.ents` if they don't overlap with
|
||
existing entities predicted by the model. To overwrite overlapping entities, you
|
||
can set `overwrite_ents=True` on initialization.
|
||
|
||
```python
|
||
### {executable="true"}
|
||
import spacy
|
||
|
||
nlp = spacy.load("en_core_web_sm")
|
||
ruler = nlp.add_pipe("entity_ruler")
|
||
patterns = [{"label": "ORG", "pattern": "MyCorp Inc."}]
|
||
ruler.add_patterns(patterns)
|
||
|
||
doc = nlp("MyCorp Inc. is a company in the U.S.")
|
||
print([(ent.text, ent.label_) for ent in doc.ents])
|
||
```
|
||
|
||
#### Validating and debugging EntityRuler patterns {#entityruler-pattern-validation new="2.1.8"}
|
||
|
||
The entity ruler can validate patterns against a JSON schema with the config
|
||
setting `"validate"`. See details under
|
||
[Validating and debugging patterns](#pattern-validation).
|
||
|
||
```python
|
||
ruler = nlp.add_pipe("entity_ruler", config={"validate": True})
|
||
```
|
||
|
||
### Adding IDs to patterns {#entityruler-ent-ids new="2.2.2"}
|
||
|
||
The [`EntityRuler`](/api/entityruler) can also accept an `id` attribute for each
|
||
pattern. Using the `id` attribute allows multiple patterns to be associated with
|
||
the same entity.
|
||
|
||
```python
|
||
### {executable="true"}
|
||
from spacy.lang.en import English
|
||
|
||
nlp = English()
|
||
ruler = nlp.add_pipe("entity_ruler")
|
||
patterns = [{"label": "ORG", "pattern": "Apple", "id": "apple"},
|
||
{"label": "GPE", "pattern": [{"LOWER": "san"}, {"LOWER": "francisco"}], "id": "san-francisco"},
|
||
{"label": "GPE", "pattern": [{"LOWER": "san"}, {"LOWER": "fran"}], "id": "san-francisco"}]
|
||
ruler.add_patterns(patterns)
|
||
|
||
doc1 = nlp("Apple is opening its first big office in San Francisco.")
|
||
print([(ent.text, ent.label_, ent.ent_id_) for ent in doc1.ents])
|
||
|
||
doc2 = nlp("Apple is opening its first big office in San Fran.")
|
||
print([(ent.text, ent.label_, ent.ent_id_) for ent in doc2.ents])
|
||
```
|
||
|
||
If the `id` attribute is included in the [`EntityRuler`](/api/entityruler)
|
||
patterns, the `ent_id_` property of the matched entity is set to the `id` given
|
||
in the patterns. So in the example above it's easy to identify that "San
|
||
Francisco" and "San Fran" are both the same entity.
|
||
|
||
### Using pattern files {#entityruler-files}
|
||
|
||
The [`to_disk`](/api/entityruler#to_disk) and
|
||
[`from_disk`](/api/entityruler#from_disk) let you save and load patterns to and
|
||
from JSONL (newline-delimited JSON) files, containing one pattern object per
|
||
line.
|
||
|
||
```json
|
||
### patterns.jsonl
|
||
{"label": "ORG", "pattern": "Apple"}
|
||
{"label": "GPE", "pattern": [{"LOWER": "san"}, {"LOWER": "francisco"}]}
|
||
```
|
||
|
||
```python
|
||
ruler.to_disk("./patterns.jsonl")
|
||
new_ruler = nlp.add_pipe("entity_ruler").from_disk("./patterns.jsonl")
|
||
```
|
||
|
||
<Infobox title="Integration with Prodigy">
|
||
|
||
If you're using the [Prodigy](https://prodi.gy) annotation tool, you might
|
||
recognize these pattern files from bootstrapping your named entity and text
|
||
classification labelling. The patterns for the `EntityRuler` follow the same
|
||
syntax, so you can use your existing Prodigy pattern files in spaCy, and vice
|
||
versa.
|
||
|
||
</Infobox>
|
||
|
||
When you save out an `nlp` object that has an `EntityRuler` added to its
|
||
pipeline, its patterns are automatically exported to the pipeline directory:
|
||
|
||
```python
|
||
nlp = spacy.load("en_core_web_sm")
|
||
ruler = nlp.add_pipe("entity_ruler")
|
||
ruler.add_patterns([{"label": "ORG", "pattern": "Apple"}])
|
||
nlp.to_disk("/path/to/pipeline")
|
||
```
|
||
|
||
The saved pipeline now includes the `"entity_ruler"` in its
|
||
[`config.cfg`](/api/data-formats#config) and the pipeline directory contains a
|
||
file `entityruler.jsonl` with the patterns. When you load the pipeline back in,
|
||
all pipeline components will be restored and deserialized – including the entity
|
||
ruler. This lets you ship powerful pipeline packages with binary weights _and_
|
||
rules included!
|
||
|
||
### Using a large number of phrase patterns {#entityruler-large-phrase-patterns new="2.2.4"}
|
||
|
||
<!-- TODO: double-check that this still works if the ruler is added to the pipeline on creation, and include suggestion if needed -->
|
||
|
||
When using a large amount of **phrase patterns** (roughly > 10000) it's useful
|
||
to understand how the `add_patterns` function of the entity ruler works. For
|
||
each **phrase pattern**, the EntityRuler calls the nlp object to construct a doc
|
||
object. This happens in case you try to add the EntityRuler at the end of an
|
||
existing pipeline with, for example, a POS tagger and want to extract matches
|
||
based on the pattern's POS signature. In this case you would pass a config value
|
||
of `"phrase_matcher_attr": "POS"` for the entity ruler.
|
||
|
||
Running the full language pipeline across every pattern in a large list scales
|
||
linearly and can therefore take a long time on large amounts of phrase patterns.
|
||
As of spaCy v2.2.4 the `add_patterns` function has been refactored to use
|
||
`nlp.pipe` on all phrase patterns resulting in about a 10x-20x speed up with
|
||
5,000-100,000 phrase patterns respectively. Even with this speedup (but
|
||
especially if you're using an older version) the `add_patterns` function can
|
||
still take a long time. An easy workaround to make this function run faster is
|
||
disabling the other language pipes while adding the phrase patterns.
|
||
|
||
```python
|
||
ruler = nlp.add_pipe("entity_ruler")
|
||
patterns = [{"label": "TEST", "pattern": str(i)} for i in range(100000)]
|
||
with nlp.select_pipes(enable="tagger"):
|
||
ruler.add_patterns(patterns)
|
||
```
|
||
|
||
## Combining models and rules {#models-rules}
|
||
|
||
You can combine statistical and rule-based components in a variety of ways.
|
||
Rule-based components can be used to improve the accuracy of statistical models,
|
||
by presetting tags, entities or sentence boundaries for specific tokens. The
|
||
statistical models will usually respect these preset annotations, which
|
||
sometimes improves the accuracy of other decisions. You can also use rule-based
|
||
components after a statistical model to correct common errors. Finally,
|
||
rule-based components can reference the attributes set by statistical models, in
|
||
order to implement more abstract logic.
|
||
|
||
### Example: Expanding named entities {#models-rules-ner}
|
||
|
||
When using a trained
|
||
[named entity recognition](/usage/linguistic-features/#named-entities) model to
|
||
extract information from your texts, you may find that the predicted span only
|
||
includes parts of the entity you're looking for. Sometimes, this happens if
|
||
statistical model predicts entities incorrectly. Other times, it happens if the
|
||
way the entity type was defined in the original training corpus doesn't match
|
||
what you need for your application.
|
||
|
||
> #### Where corpora come from
|
||
>
|
||
> Corpora used to train pipelines from scratch are often produced in academia.
|
||
> They contain text from various sources with linguistic features labeled
|
||
> manually by human annotators (following a set of specific guidelines). The
|
||
> corpora are then distributed with evaluation data, so other researchers can
|
||
> benchmark their algorithms and everyone can report numbers on the same data.
|
||
> However, most applications need to learn information that isn't contained in
|
||
> any available corpus.
|
||
|
||
For example, the corpus spaCy's [English pipelines](/models/en) were trained on
|
||
defines a `PERSON` entity as just the **person name**, without titles like "Mr."
|
||
or "Dr.". This makes sense, because it makes it easier to resolve the entity
|
||
type back to a knowledge base. But what if your application needs the full
|
||
names, _including_ the titles?
|
||
|
||
```python
|
||
### {executable="true"}
|
||
import spacy
|
||
|
||
nlp = spacy.load("en_core_web_sm")
|
||
doc = nlp("Dr. Alex Smith chaired first board meeting of Acme Corp Inc.")
|
||
print([(ent.text, ent.label_) for ent in doc.ents])
|
||
```
|
||
|
||
While you could try and teach the model a new definition of the `PERSON` entity
|
||
by [updating it](/usage/training/#example-train-ner) with more examples of spans
|
||
that include the title, this might not be the most efficient approach. The
|
||
existing model was trained on over 2 million words, so in order to completely
|
||
change the definition of an entity type, you might need a lot of training
|
||
examples. However, if you already have the predicted `PERSON` entities, you can
|
||
use a rule-based approach that checks whether they come with a title and if so,
|
||
expands the entity span by one token. After all, what all titles in this example
|
||
have in common is that _if_ they occur, they occur in the **previous token**
|
||
right before the person entity.
|
||
|
||
```python
|
||
### {highlight="9-13"}
|
||
from spacy.language import Language
|
||
from spacy.tokens import Span
|
||
|
||
@Language.component("expand_person_entities")
|
||
def expand_person_entities(doc):
|
||
new_ents = []
|
||
for ent in doc.ents:
|
||
# Only check for title if it's a person and not the first token
|
||
if ent.label_ == "PERSON" and ent.start != 0:
|
||
prev_token = doc[ent.start - 1]
|
||
if prev_token.text in ("Dr", "Dr.", "Mr", "Mr.", "Ms", "Ms."):
|
||
new_ent = Span(doc, ent.start - 1, ent.end, label=ent.label)
|
||
new_ents.append(new_ent)
|
||
else:
|
||
new_ents.append(ent)
|
||
else:
|
||
new_ents.append(ent)
|
||
doc.ents = new_ents
|
||
return doc
|
||
```
|
||
|
||
The above function takes a `Doc` object, modifies its `doc.ents` and returns it.
|
||
Using the [`@Language.component`](/api/language#component) decorator, we can
|
||
register it as a [pipeline component](/usage/processing-pipelines) so it can run
|
||
automatically when processing a text. We can use
|
||
[`nlp.add_pipe`](/api/language#add_pipe) to add it to the current pipeline.
|
||
|
||
```python
|
||
### {executable="true"}
|
||
import spacy
|
||
from spacy.language import Language
|
||
from spacy.tokens import Span
|
||
|
||
nlp = spacy.load("en_core_web_sm")
|
||
|
||
@Language.component("expand_person_entities")
|
||
def expand_person_entities(doc):
|
||
new_ents = []
|
||
for ent in doc.ents:
|
||
if ent.label_ == "PERSON" and ent.start != 0:
|
||
prev_token = doc[ent.start - 1]
|
||
if prev_token.text in ("Dr", "Dr.", "Mr", "Mr.", "Ms", "Ms."):
|
||
new_ent = Span(doc, ent.start - 1, ent.end, label=ent.label)
|
||
new_ents.append(new_ent)
|
||
else:
|
||
new_ents.append(ent)
|
||
doc.ents = new_ents
|
||
return doc
|
||
|
||
# Add the component after the named entity recognizer
|
||
nlp.add_pipe("expand_person_entities", after="ner")
|
||
|
||
doc = nlp("Dr. Alex Smith chaired first board meeting of Acme Corp Inc.")
|
||
print([(ent.text, ent.label_) for ent in doc.ents])
|
||
```
|
||
|
||
An alternative approach would be to use an
|
||
[extension attribute](/usage/processing-pipelines/#custom-components-attributes)
|
||
like `._.person_title` and add it to `Span` objects (which includes entity spans
|
||
in `doc.ents`). The advantage here is that the entity text stays intact and can
|
||
still be used to look up the name in a knowledge base. The following function
|
||
takes a `Span` object, checks the previous token if it's a `PERSON` entity and
|
||
returns the title if one is found. The `Span.doc` attribute gives us easy access
|
||
to the span's parent document.
|
||
|
||
```python
|
||
def get_person_title(span):
|
||
if span.label_ == "PERSON" and span.start != 0:
|
||
prev_token = span.doc[span.start - 1]
|
||
if prev_token.text in ("Dr", "Dr.", "Mr", "Mr.", "Ms", "Ms."):
|
||
return prev_token.text
|
||
```
|
||
|
||
We can now use the [`Span.set_extension`](/api/span#set_extension) method to add
|
||
the custom extension attribute `"person_title"`, using `get_person_title` as the
|
||
getter function.
|
||
|
||
```python
|
||
### {executable="true"}
|
||
import spacy
|
||
from spacy.tokens import Span
|
||
|
||
nlp = spacy.load("en_core_web_sm")
|
||
|
||
def get_person_title(span):
|
||
if span.label_ == "PERSON" and span.start != 0:
|
||
prev_token = span.doc[span.start - 1]
|
||
if prev_token.text in ("Dr", "Dr.", "Mr", "Mr.", "Ms", "Ms."):
|
||
return prev_token.text
|
||
|
||
# Register the Span extension as 'person_title'
|
||
Span.set_extension("person_title", getter=get_person_title)
|
||
|
||
doc = nlp("Dr Alex Smith chaired first board meeting of Acme Corp Inc.")
|
||
print([(ent.text, ent.label_, ent._.person_title) for ent in doc.ents])
|
||
```
|
||
|
||
### Example: Using entities, part-of-speech tags and the dependency parse {#models-rules-pos-dep}
|
||
|
||
> #### Linguistic features
|
||
>
|
||
> This example makes extensive use of part-of-speech tag and dependency
|
||
> attributes and related `Doc`, `Token` and `Span` methods. For an introduction
|
||
> on this, see the guide on [linguistic features](/usage/linguistic-features/).
|
||
> Also see the label schemes in the [models directory](/models) for details on
|
||
> the labels.
|
||
|
||
Let's say you want to parse professional biographies and extract the person
|
||
names and company names, and whether it's a company they're _currently_ working
|
||
at, or a _previous_ company. One approach could be to try and train a named
|
||
entity recognizer to predict `CURRENT_ORG` and `PREVIOUS_ORG` – but this
|
||
distinction is very subtle and something the entity recognizer may struggle to
|
||
learn. Nothing about "Acme Corp Inc." is inherently "current" or "previous".
|
||
|
||
However, the syntax of the sentence holds some very important clues: we can
|
||
check for trigger words like "work", whether they're **past tense** or **present
|
||
tense**, whether company names are attached to it and whether the person is the
|
||
subject. All of this information is available in the part-of-speech tags and the
|
||
dependency parse.
|
||
|
||
```python
|
||
### {executable="true"}
|
||
import spacy
|
||
|
||
nlp = spacy.load("en_core_web_sm")
|
||
doc = nlp("Alex Smith worked at Acme Corp Inc.")
|
||
print([(ent.text, ent.label_) for ent in doc.ents])
|
||
```
|
||
|
||
> - `nsubj`: Nominal subject.
|
||
> - `prep`: Preposition.
|
||
> - `pobj`: Object of preposition.
|
||
> - `NNP`: Proper noun, singular.
|
||
> - `VBD`: Verb, past tense.
|
||
> - `IN`: Conjunction, subordinating or preposition.
|
||
|
||
|
||
|
||
In this example, "worked" is the root of the sentence and is a past tense verb.
|
||
Its subject is "Alex Smith", the person who worked. "at Acme Corp Inc." is a
|
||
prepositional phrase attached to the verb "worked". To extract this
|
||
relationship, we can start by looking at the predicted `PERSON` entities, find
|
||
their heads and check whether they're attached to a trigger word like "work".
|
||
Next, we can check for prepositional phrases attached to the head and whether
|
||
they contain an `ORG` entity. Finally, to determine whether the company
|
||
affiliation is current, we can check the head's part-of-speech tag.
|
||
|
||
```python
|
||
person_entities = [ent for ent in doc.ents if ent.label_ == "PERSON"]
|
||
for ent in person_entities:
|
||
# Because the entity is a span, we need to use its root token. The head
|
||
# is the syntactic governor of the person, e.g. the verb
|
||
head = ent.root.head
|
||
if head.lemma_ == "work":
|
||
# Check if the children contain a preposition
|
||
preps = [token for token in head.children if token.dep_ == "prep"]
|
||
for prep in preps:
|
||
# Check if tokens part of ORG entities are in the preposition's
|
||
# children, e.g. at -> Acme Corp Inc.
|
||
orgs = [token for token in prep.children if token.ent_type_ == "ORG"]
|
||
# If the verb is in past tense, the company was a previous company
|
||
print({"person": ent, "orgs": orgs, "past": head.tag_ == "VBD"})
|
||
```
|
||
|
||
To apply this logic automatically when we process a text, we can add it to the
|
||
`nlp` object as a
|
||
[custom pipeline component](/usage/processing-pipelines/#custom-components). The
|
||
above logic also expects that entities are merged into single tokens. spaCy
|
||
ships with a handy built-in `merge_entities` that takes care of that. Instead of
|
||
just printing the result, you could also write it to
|
||
[custom attributes](/usage/processing-pipelines#custom-components-attributes) on
|
||
the entity `Span` – for example `._.orgs` or `._.prev_orgs` and
|
||
`._.current_orgs`.
|
||
|
||
> #### Merging entities
|
||
>
|
||
> Under the hood, entities are merged using the
|
||
> [`Doc.retokenize`](/api/doc#retokenize) context manager:
|
||
>
|
||
> ```python
|
||
> with doc.retokenize() as retokenize:
|
||
> for ent in doc.ents:
|
||
> retokenizer.merge(ent)
|
||
> ```
|
||
|
||
```python
|
||
### {executable="true"}
|
||
import spacy
|
||
from spacy.language import Language
|
||
from spacy import displacy
|
||
|
||
nlp = spacy.load("en_core_web_sm")
|
||
|
||
@Language.component("extract_person_orgs")
|
||
def extract_person_orgs(doc):
|
||
person_entities = [ent for ent in doc.ents if ent.label_ == "PERSON"]
|
||
for ent in person_entities:
|
||
head = ent.root.head
|
||
if head.lemma_ == "work":
|
||
preps = [token for token in head.children if token.dep_ == "prep"]
|
||
for prep in preps:
|
||
orgs = [token for token in prep.children if token.ent_type_ == "ORG"]
|
||
print({'person': ent, 'orgs': orgs, 'past': head.tag_ == "VBD"})
|
||
return doc
|
||
|
||
# To make the entities easier to work with, we'll merge them into single tokens
|
||
nlp.add_pipe("merge_entities")
|
||
nlp.add_pipe("extract_person_orgs")
|
||
|
||
doc = nlp("Alex Smith worked at Acme Corp Inc.")
|
||
# If you're not in a Jupyter / IPython environment, use displacy.serve
|
||
displacy.render(doc, options={"fine_grained": True})
|
||
```
|
||
|
||
If you change the sentence structure above, for example to "was working", you'll
|
||
notice that our current logic fails and doesn't correctly detect the company as
|
||
a past organization. That's because the root is a participle and the tense
|
||
information is in the attached auxiliary "was":
|
||
|
||
|
||
|
||
To solve this, we can adjust the rules to also check for the above construction:
|
||
|
||
```python
|
||
### {highlight="10-12"}
|
||
@Language.component("extract_person_orgs")
|
||
def extract_person_orgs(doc):
|
||
person_entities = [ent for ent in doc.ents if ent.label_ == "PERSON"]
|
||
for ent in person_entities:
|
||
head = ent.root.head
|
||
if head.lemma_ == "work":
|
||
preps = [token for token in head.children if token.dep_ == "prep"]
|
||
for prep in preps:
|
||
orgs = [t for t in prep.children if t.ent_type_ == "ORG"]
|
||
aux = [token for token in head.children if token.dep_ == "aux"]
|
||
past_aux = any(t.tag_ == "VBD" for t in aux)
|
||
past = head.tag_ == "VBD" or head.tag_ == "VBG" and past_aux
|
||
print({'person': ent, 'orgs': orgs, 'past': past})
|
||
return doc
|
||
```
|
||
|
||
In your final rule-based system, you may end up with **several different code
|
||
paths** to cover the types of constructions that occur in your data.
|