--- title: Rule-based matching teaser: Find phrases and tokens, and match entities menu: - ['Token Matcher', 'matcher'] - ['Phrase Matcher', 'phrasematcher'] - ['Entity Ruler', 'entityruler'] - ['Models & Rules', 'models-rules'] --- Compared to using regular expressions on raw text, spaCy's rule-based matcher engines and components not only let you find the words and phrases you're looking for – they also give you access to the tokens within the document and their relationships. This means you can easily access and analyze the surrounding tokens, merge spans into single tokens or add entries to the named entities in `doc.ents`. For complex tasks, it's usually better to train a statistical entity recognition model. However, statistical models require training data, so for many situations, rule-based approaches are more practical. This is especially true at the start of a project: you can use a rule-based approach as part of a data collection process, to help you "bootstrap" a statistical model. Training a model is useful if you have some examples and you want your system to be able to **generalize** based on those examples. It works especially well if there are clues in the _local context_. For instance, if you're trying to detect person or company names, your application may benefit from a statistical named entity recognition model. Rule-based systems are a good choice if there's a more or less **finite number** of examples that you want to find in the data, or if there's a very **clear, structured pattern** you can express with token rules or regular expressions. For instance, country names, IP addresses or URLs are things you might be able to handle well with a purely rule-based approach. You can also combine both approaches and improve a statistical model with rules to handle very specific cases and boost accuracy. For details, see the section on [rule-based entity recognition](#entityruler). The `PhraseMatcher` is useful if you already have a large terminology list or gazetteer consisting of single or multi-token phrases that you want to find exact instances of in your data. As of spaCy v2.1.0, you can also match on the `LOWER` attribute for fast and case-insensitive matching. The `Matcher` isn't as blazing fast as the `PhraseMatcher`, since it compares across individual token attributes. However, it allows you to write very abstract representations of the tokens you're looking for, using lexical attributes, linguistic features predicted by the model, operators, set membership and rich comparison. For example, you can find a noun, followed by a verb with the lemma "love" or "like", followed by an optional determiner and another token that's at least ten characters long. ## Token-based matching {#matcher} spaCy features a rule-matching engine, the [`Matcher`](/api/matcher), that operates over tokens, similar to regular expressions. The rules can refer to token annotations (e.g. the token `text` or `tag_`, and flags (e.g. `IS_PUNCT`). The rule matcher also lets you pass in a custom callback to act on matches – for example, to merge entities and apply custom labels. You can also associate patterns with entity IDs, to allow some basic entity linking or disambiguation. To match large terminology lists, you can use the [`PhraseMatcher`](/api/phrasematcher), which accepts `Doc` objects as match patterns. ### Adding patterns {#adding-patterns} Let's say we want to enable spaCy to find a combination of three tokens: 1. A token whose **lowercase form matches "hello"**, e.g. "Hello" or "HELLO". 2. A token whose **`is_punct` flag is set to `True`**, i.e. any punctuation. 3. A token whose **lowercase form matches "world"**, e.g. "World" or "WORLD". ```python [{"LOWER": "hello"}, {"IS_PUNCT": True}, {"LOWER": "world"}] ``` When writing patterns, keep in mind that **each dictionary** represents **one token**. If spaCy's tokenization doesn't match the tokens defined in a pattern, the pattern is not going to produce any results. When developing complex patterns, make sure to check examples against spaCy's tokenization: ```python doc = nlp("A complex-example,!") print([token.text for token in doc]) ``` First, we initialize the `Matcher` with a vocab. The matcher must always share the same vocab with the documents it will operate on. We can now call [`matcher.add()`](/api/matcher#add) with an ID and a list of patterns. ```python ### {executable="true"} import spacy from spacy.matcher import Matcher nlp = spacy.load("en_core_web_sm") matcher = Matcher(nlp.vocab) # Add match ID "HelloWorld" with no callback and one pattern pattern = [{"LOWER": "hello"}, {"IS_PUNCT": True}, {"LOWER": "world"}] matcher.add("HelloWorld", [pattern]) doc = nlp("Hello, world! Hello world!") matches = matcher(doc) for match_id, start, end in matches: string_id = nlp.vocab.strings[match_id] # Get string representation span = doc[start:end] # The matched span print(match_id, string_id, start, end, span.text) ``` The matcher returns a list of `(match_id, start, end)` tuples – in this case, `[('15578876784678163569', 0, 3)]`, which maps to the span `doc[0:3]` of our original document. The `match_id` is the [hash value](/usage/spacy-101#vocab) of the string ID "HelloWorld". To get the string value, you can look up the ID in the [`StringStore`](/api/stringstore). ```python for match_id, start, end in matches: string_id = nlp.vocab.strings[match_id] # 'HelloWorld' span = doc[start:end] # The matched span ``` Optionally, we could also choose to add more than one pattern, for example to also match sequences without punctuation between "hello" and "world": ```python patterns = [ [{"LOWER": "hello"}, {"IS_PUNCT": True}, {"LOWER": "world"}], [{"LOWER": "hello"}, {"LOWER": "world"}] ] matcher.add("HelloWorld", patterns) ``` By default, the matcher will only return the matches and **not do anything else**, like merge entities or assign labels. This is all up to you and can be defined individually for each pattern, by passing in a callback function as the `on_match` argument on `add()`. This is useful, because it lets you write entirely custom and **pattern-specific logic**. For example, you might want to merge _some_ patterns into one token, while adding entity labels for other pattern types. You shouldn't have to create different matchers for each of those processes. #### Available token attributes {#adding-patterns-attributes} The available token pattern keys correspond to a number of [`Token` attributes](/api/token#attributes). The supported attributes for rule-based matching are: | Attribute |  Description | | -------------------------------------- | ------------------------------------------------------------------------------------------------------------------------- | | `ORTH` | The exact verbatim text of a token. ~~str~~ | | `TEXT` 2.1 | The exact verbatim text of a token. ~~str~~ | | `LOWER` | The lowercase form of the token text. ~~str~~ | |  `LENGTH` | The length of the token text. ~~int~~ | |  `IS_ALPHA`, `IS_ASCII`, `IS_DIGIT` | Token text consists of alphabetic characters, ASCII characters, digits. ~~bool~~ | |  `IS_LOWER`, `IS_UPPER`, `IS_TITLE` | Token text is in lowercase, uppercase, titlecase. ~~bool~~ | |  `IS_PUNCT`, `IS_SPACE`, `IS_STOP` | Token is punctuation, whitespace, stop word. ~~bool~~ | |  `LIKE_NUM`, `LIKE_URL`, `LIKE_EMAIL` | Token text resembles a number, URL, email. ~~bool~~ | |  `POS`, `TAG`, `DEP`, `LEMMA`, `SHAPE` | The token's simple and extended part-of-speech tag, dependency label, lemma, shape. ~~str~~ | | `ENT_TYPE` | The token's entity label. ~~str~~ | | `_` 2.1 | Properties in [custom extension attributes](/usage/processing-pipelines#custom-components-attributes). ~~Dict[str, Any]~~ | | `OP` | [Operator or quantifier](#quantifiers) to determine how often to match a token pattern. ~~str~~ | No, it shouldn't. spaCy will normalize the names internally and `{"LOWER": "text"}` and `{"lower": "text"}` will both produce the same result. Using the uppercase version is mostly a convention to make it clear that the attributes are "special" and don't exactly map to the token attributes like `Token.lower` and `Token.lower_`. spaCy can't provide access to all of the attributes because the `Matcher` loops over the Cython data, not the Python objects. Inside the matcher, we're dealing with a [`TokenC` struct](/api/cython-structs#tokenc) – we don't have an instance of [`Token`](/api/token). This means that all of the attributes that refer to computed properties can't be accessed. The uppercase attribute names like `LOWER` or `IS_PUNCT` refer to symbols from the [`spacy.attrs`](https://github.com/explosion/spaCy/tree/master/spacy/attrs.pyx) enum table. They're passed into a function that essentially is a big case/switch statement, to figure out which struct field to return. The same attribute identifiers are used in [`Doc.to_array`](/api/doc#to_array), and a few other places in the code where you need to describe fields like this. --- [![Matcher demo](../images/matcher-demo.jpg)](https://explosion.ai/demos/matcher) The [Matcher Explorer](https://explosion.ai/demos/matcher) lets you test the rule-based `Matcher` by creating token patterns interactively and running them over your text. Each token can set multiple attributes like text value, part-of-speech tag or boolean flags. The token-based view lets you explore how spaCy processes your text – and why your pattern matches, or why it doesn't. #### Extended pattern syntax and attributes {#adding-patterns-attributes-extended new="2.1"} Instead of mapping to a single value, token patterns can also map to a **dictionary of properties**. For example, to specify that the value of a lemma should be part of a list of values, or to set a minimum character length. The following rich comparison attributes are available: > #### Example > > ```python > # Matches "love cats" or "likes flowers" > pattern1 = [{"LEMMA": {"IN": ["like", "love"]}}, > {"POS": "NOUN"}] > > # Matches tokens of length >= 10 > pattern2 = [{"LENGTH": {">=": 10}}] > ``` | Attribute | Description | | -------------------------- | ------------------------------------------------------------------------------------------------------- | | `IN` | Attribute value is member of a list. ~~Any~~ | | `NOT_IN` | Attribute value is _not_ member of a list. ~~Any~~ | | `==`, `>=`, `<=`, `>`, `<` | Attribute value is equal, greater or equal, smaller or equal, greater or smaller. ~~Union[int, float]~~ | #### Regular expressions {#regex new="2.1"} In some cases, only matching tokens and token attributes isn't enough – for example, you might want to match different spellings of a word, without having to add a new pattern for each spelling. ```python pattern = [{"TEXT": {"REGEX": "^[Uu](\\.?|nited)$"}}, {"TEXT": {"REGEX": "^[Ss](\\.?|tates)$"}}, {"LOWER": "president"}] ``` The `REGEX` operator allows defining rules for any attribute string value, including custom attributes. It always needs to be applied to an attribute like `TEXT`, `LOWER` or `TAG`: ```python # Match different spellings of token texts pattern = [{"TEXT": {"REGEX": "deff?in[ia]tely"}}] # Match tokens with fine-grained POS tags starting with 'V' pattern = [{"TAG": {"REGEX": "^V"}}] # Match custom attribute values with regular expressions pattern = [{"_": {"country": {"REGEX": "^[Uu](nited|\\.?) ?[Ss](tates|\\.?)$"}}}] ``` When using the `REGEX` operator, keep in mind that it operates on **single tokens**, not the whole text. Each expression you provide will be matched on a token. If you need to match on the whole text instead, see the details on [regex matching on the whole text](#regex-text). ##### Matching regular expressions on the full text {#regex-text} If your expressions apply to multiple tokens, a simple solution is to match on the `doc.text` with `re.finditer` and use the [`Doc.char_span`](/api/doc#char_span) method to create a `Span` from the character indices of the match. If the matched characters don't map to one or more valid tokens, `Doc.char_span` returns `None`. > #### What's a valid token sequence? > > In the example, the expression will also match `"US"` in `"USA"`. However, > `"USA"` is a single token and `Span` objects are **sequences of tokens**. So > `"US"` cannot be its own span, because it does not end on a token boundary. ```python ### {executable="true"} import spacy import re nlp = spacy.load("en_core_web_sm") doc = nlp("The United States of America (USA) are commonly known as the United States (U.S. or US) or America.") expression = r"[Uu](nited|\\.?) ?[Ss](tates|\\.?)" for match in re.finditer(expression, doc.text): start, end = match.span() span = doc.char_span(start, end) # This is a Span object or None if match doesn't map to valid token sequence if span is not None: print("Found match:", span.text) ``` In some cases, you might want to expand the match to the closest token boundaries, so you can create a `Span` for `"USA"`, even though only the substring `"US"` is matched. You can calculate this using the character offsets of the tokens in the document, available as [`Token.idx`](/api/token#attributes). This lets you create a list of valid token start and end boundaries and leaves you with a rather basic algorithmic problem: Given a number, find the next lowest (start token) or the next highest (end token) number that's part of a given list of numbers. This will be the closest valid token boundary. There are many ways to do this and the most straightforward one is to create a dict keyed by characters in the `Doc`, mapped to the token they're part of. It's easy to write and less error-prone, and gives you a constant lookup time: you only ever need to create the dict once per `Doc`. ```python chars_to_tokens = {} for token in doc: for i in range(token.idx, token.idx + len(token.text)): chars_to_tokens[i] = token.i ``` You can then look up character at a given position, and get the index of the corresponding token that the character is part of. Your span would then be `doc[token_start:token_end]`. If a character isn't in the dict, it means it's the (white)space tokens are split on. That hopefully shouldn't happen, though, because it'd mean your regex is producing matches with leading or trailing whitespace. ```python ### {highlight="5-8"} span = doc.char_span(start, end) if span is not None: print("Found match:", span.text) else: start_token = chars_to_tokens.get(start) end_token = chars_to_tokens.get(end) if start_token is not None and end_token is not None: span = doc[start_token:end_token + 1] print("Found closest match:", span.text) ``` --- #### Operators and quantifiers {#quantifiers} The matcher also lets you use quantifiers, specified as the `'OP'` key. Quantifiers let you define sequences of tokens to be matched, e.g. one or more punctuation marks, or specify optional tokens. Note that there are no nested or scoped quantifiers – instead, you can build those behaviors with `on_match` callbacks. | OP | Description | | --- | ---------------------------------------------------------------- | | `!` | Negate the pattern, by requiring it to match exactly 0 times. | | `?` | Make the pattern optional, by allowing it to match 0 or 1 times. | | `+` | Require the pattern to match 1 or more times. | | `*` | Allow the pattern to match zero or more times. | > #### Example > > ```python > pattern = [{"LOWER": "hello"}, > {"IS_PUNCT": True, "OP": "?"}] > ``` In versions before v2.1.0, the semantics of the `+` and `*` operators behave inconsistently. They were usually interpreted "greedily", i.e. longer matches are returned where possible. However, if you specify two `+` and `*` patterns in a row and their matches overlap, the first operator will behave non-greedily. This quirk in the semantics is corrected in spaCy v2.1.0. #### Using wildcard token patterns {#adding-patterns-wildcard new="2"} While the token attributes offer many options to write highly specific patterns, 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 say you're trying to extract people's user names from your data. All you know is that they are listed as "User name: {username}". The name itself may contain any character, but no whitespace – so you'll know it will be handled as one token. ```python [{"ORTH": "User"}, {"ORTH": "name"}, {"ORTH": ":"}, {}] ``` #### Validating and debugging patterns {#pattern-validation new="2.1"} The `Matcher` can validate patterns against a JSON schema with the option `validate=True`. This is useful for debugging patterns during development, in particular for catching unsupported attributes. ```python ### {executable="true"} import spacy from spacy.matcher import Matcher nlp = spacy.load("en_core_web_sm") 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: # - Additional properties are not allowed ('CASEINSENSITIVE' was unexpected) [2] ``` ### 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, in case someone has written it 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. `
` or `
`). 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
world!
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"}) ``` For more details and examples of how to **create custom pipeline components** and **extension attributes**, see the [usage guide](/usage/processing-pipelines). ### 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 model 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", None, [{"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. To create the patterns, each phrase has to be processed with the `nlp` object. If you have a model 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)) ``` ### 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]) ``` 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 are 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`. 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. 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 string 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. ## Rule-based entity recognition {#entityruler new="2.1"} The [`EntityRuler`](/api/entityruler) is an exciting new component that lets you add named entities based on pattern dictionaries, and makes it easy to combine rule-based and statistical named entity recognition for even more powerful models. ### 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 statistical models 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") ``` 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. When you save out an `nlp` object that has an `EntityRuler` added to its pipeline, its patterns are automatically exported to the model 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/model") ``` The saved model now includes the `"entity_ruler"` in its [`config.cfg`](/api/data-formats#config) and the model directory contains a file `entityruler.jsonl` with the patterns. When you load the model back in, all pipeline components will be restored and deserialized – including the entity ruler. This lets you ship powerful model packages with binary weights _and_ rules included! ### Using a large number of phrase patterns {#entityruler-large-phrase-patterns new="2.2.4"} 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 2.2.4 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 the a pretrained [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 way defined in the original training corpus doesn't match what you need for your application. > #### Where corpora come from > > Corpora used to train models 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 models](/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 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. ![Visualization of dependency parse](../images/displacy-model-rules.svg "[`spacy.displacy`](/api/top-level#displacy) visualization with `options={'fine_grained': True}` to output the fine-grained part-of-speech tags, i.e. `Token.tag_`") 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 spans, 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": ![Visualization of dependency parse](../images/displacy-model-rules2.svg) 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.