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329 lines
16 KiB
Markdown
329 lines
16 KiB
Markdown
---
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title: Lemmatizer
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tag: class
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source: spacy/pipeline/lemmatizer.py
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new: 3
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teaser: 'Pipeline component for lemmatization'
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api_string_name: lemmatizer
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api_trainable: false
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---
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Component for assigning base forms to tokens using rules based on part-of-speech
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tags, or lookup tables. Different [`Language`](/api/language) subclasses can
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implement their own lemmatizer components via
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[language-specific factories](/usage/processing-pipelines#factories-language).
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The default data used is provided by the
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[`spacy-lookups-data`](https://github.com/explosion/spacy-lookups-data)
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extension package.
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For a trainable lemmatizer, see [`EditTreeLemmatizer`](/api/edittreelemmatizer).
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<Infobox variant="warning" title="New in v3.0">
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As of v3.0, the `Lemmatizer` is a **standalone pipeline component** that can be
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added to your pipeline, and not a hidden part of the vocab that runs behind the
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scenes. This makes it easier to customize how lemmas should be assigned in your
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pipeline.
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If the lemmatization mode is set to `"rule"`, which requires coarse-grained POS
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(`Token.pos`) to be assigned, make sure a [`Tagger`](/api/tagger),
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[`Morphologizer`](/api/morphologizer) or another component assigning POS is
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available in the pipeline and runs _before_ the lemmatizer.
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</Infobox>
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## Assigned Attributes {#assigned-attributes}
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Lemmas generated by rules or predicted will be saved to `Token.lemma`.
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| Location | Value |
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| -------------- | ------------------------- |
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| `Token.lemma` | The lemma (hash). ~~int~~ |
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| `Token.lemma_` | The lemma. ~~str~~ |
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## Config and implementation
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The default config is defined by the pipeline component factory and describes
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how the component should be configured. You can override its settings via the
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`config` argument on [`nlp.add_pipe`](/api/language#add_pipe) or in your
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[`config.cfg` for training](/usage/training#config). For examples of the lookups
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data format used by the lookup and rule-based lemmatizers, see
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[`spacy-lookups-data`](https://github.com/explosion/spacy-lookups-data).
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> #### Example
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>
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> ```python
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> config = {"mode": "rule"}
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> nlp.add_pipe("lemmatizer", config=config)
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> ```
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| Setting | Description |
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| -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| `mode` | The lemmatizer mode, e.g. `"lookup"` or `"rule"`. Defaults to `lookup` if no language-specific lemmatizer is available (see the following table). ~~str~~ |
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| `overwrite` | Whether to overwrite existing lemmas. Defaults to `False`. ~~bool~~ |
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| `model` | **Not yet implemented:** the model to use. ~~Model~~ |
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| _keyword-only_ | |
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| `scorer` | The scoring method. Defaults to [`Scorer.score_token_attr`](/api/scorer#score_token_attr) for the attribute `"lemma"`. ~~Optional[Callable]~~ |
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Many languages specify a default lemmatizer mode other than `lookup` if a better
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lemmatizer is available. The lemmatizer modes `rule` and `pos_lookup` require
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[`token.pos`](/api/token) from a previous pipeline component (see example
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pipeline configurations in the
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[pretrained pipeline design details](/models#design-cnn)) or rely on third-party
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libraries (`pymorphy3`).
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| Language | Default Mode |
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| -------- | ------------ |
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| `bn` | `rule` |
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| `ca` | `pos_lookup` |
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| `el` | `rule` |
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| `en` | `rule` |
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| `es` | `rule` |
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| `fa` | `rule` |
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| `fr` | `rule` |
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| `it` | `pos_lookup` |
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| `mk` | `rule` |
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| `nb` | `rule` |
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| `nl` | `rule` |
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| `pl` | `pos_lookup` |
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| `ru` | `pymorphy3` |
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| `sv` | `rule` |
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| `uk` | `pymorphy3` |
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```python
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%%GITHUB_SPACY/spacy/pipeline/lemmatizer.py
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```
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## Lemmatizer.\_\_init\_\_ {#init tag="method"}
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> #### Example
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>
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> ```python
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> # Construction via add_pipe with default model
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> lemmatizer = nlp.add_pipe("lemmatizer")
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>
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> # Construction via add_pipe with custom settings
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> config = {"mode": "rule", "overwrite": True}
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> lemmatizer = nlp.add_pipe("lemmatizer", config=config)
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> ```
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Create a new pipeline instance. In your application, you would normally use a
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shortcut for this and instantiate the component using its string name and
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[`nlp.add_pipe`](/api/language#add_pipe).
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| Name | Description |
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| -------------- | --------------------------------------------------------------------------------------------------- |
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| `vocab` | The shared vocabulary. ~~Vocab~~ |
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| `model` | **Not yet implemented:** The model to use. ~~Model~~ |
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| `name` | String name of the component instance. Used to add entries to the `losses` during training. ~~str~~ |
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| _keyword-only_ | |
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| mode | The lemmatizer mode, e.g. `"lookup"` or `"rule"`. Defaults to `"lookup"`. ~~str~~ |
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| overwrite | Whether to overwrite existing lemmas. ~~bool~~ |
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## Lemmatizer.\_\_call\_\_ {#call tag="method"}
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Apply the pipe to one document. The document is modified in place, and returned.
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This usually happens under the hood when the `nlp` object is called on a text
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and all pipeline components are applied to the `Doc` in order.
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> #### Example
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>
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> ```python
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> doc = nlp("This is a sentence.")
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> lemmatizer = nlp.add_pipe("lemmatizer")
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> # This usually happens under the hood
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> processed = lemmatizer(doc)
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> ```
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| Name | Description |
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| ----------- | -------------------------------- |
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| `doc` | The document to process. ~~Doc~~ |
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| **RETURNS** | The processed document. ~~Doc~~ |
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## Lemmatizer.pipe {#pipe tag="method"}
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Apply the pipe to a stream of documents. This usually happens under the hood
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when the `nlp` object is called on a text and all pipeline components are
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applied to the `Doc` in order.
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> #### Example
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>
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> ```python
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> lemmatizer = nlp.add_pipe("lemmatizer")
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> for doc in lemmatizer.pipe(docs, batch_size=50):
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> pass
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> ```
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| Name | Description |
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| -------------- | ------------------------------------------------------------- |
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| `stream` | A stream of documents. ~~Iterable[Doc]~~ |
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| _keyword-only_ | |
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| `batch_size` | The number of documents to buffer. Defaults to `128`. ~~int~~ |
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| **YIELDS** | The processed documents in order. ~~Doc~~ |
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## Lemmatizer.initialize {#initialize tag="method"}
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Initialize the lemmatizer and load any data resources. This method is typically
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called by [`Language.initialize`](/api/language#initialize) and lets you
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customize arguments it receives via the
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[`[initialize.components]`](/api/data-formats#config-initialize) block in the
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config. The loading only happens during initialization, typically before
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training. At runtime, all data is loaded from disk.
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> #### Example
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>
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> ```python
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> lemmatizer = nlp.add_pipe("lemmatizer")
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> lemmatizer.initialize(lookups=lookups)
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> ```
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>
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> ```ini
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> ### config.cfg
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> [initialize.components.lemmatizer]
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>
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> [initialize.components.lemmatizer.lookups]
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> @misc = "load_my_lookups.v1"
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> ```
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| Name | Description |
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| -------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| `get_examples` | Function that returns gold-standard annotations in the form of [`Example`](/api/example) objects. Defaults to `None`. ~~Optional[Callable[[], Iterable[Example]]]~~ |
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| _keyword-only_ | |
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| `nlp` | The current `nlp` object. Defaults to `None`. ~~Optional[Language]~~ |
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| `lookups` | The lookups object containing the tables such as `"lemma_rules"`, `"lemma_index"`, `"lemma_exc"` and `"lemma_lookup"`. If `None`, default tables are loaded from [`spacy-lookups-data`](https://github.com/explosion/spacy-lookups-data). Defaults to `None`. ~~Optional[Lookups]~~ |
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## Lemmatizer.lookup_lemmatize {#lookup_lemmatize tag="method"}
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Lemmatize a token using a lookup-based approach. If no lemma is found, the
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original string is returned.
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| Name | Description |
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| ----------- | --------------------------------------------------- |
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| `token` | The token to lemmatize. ~~Token~~ |
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| **RETURNS** | A list containing one or more lemmas. ~~List[str]~~ |
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## Lemmatizer.rule_lemmatize {#rule_lemmatize tag="method"}
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Lemmatize a token using a rule-based approach. Typically relies on POS tags.
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| Name | Description |
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| ----------- | --------------------------------------------------- |
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| `token` | The token to lemmatize. ~~Token~~ |
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| **RETURNS** | A list containing one or more lemmas. ~~List[str]~~ |
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## Lemmatizer.is_base_form {#is_base_form tag="method"}
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Check whether we're dealing with an uninflected paradigm, so we can avoid
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lemmatization entirely.
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| Name | Description |
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| ----------- | ---------------------------------------------------------------------------------------------------------------- |
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| `token` | The token to analyze. ~~Token~~ |
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| **RETURNS** | Whether the token's attributes (e.g., part-of-speech tag, morphological features) describe a base form. ~~bool~~ |
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## Lemmatizer.get_lookups_config {#get_lookups_config tag="classmethod"}
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Returns the lookups configuration settings for a given mode for use in
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[`Lemmatizer.load_lookups`](/api/lemmatizer#load_lookups).
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| Name | Description |
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| ----------- | -------------------------------------------------------------------------------------- |
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| `mode` | The lemmatizer mode. ~~str~~ |
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| **RETURNS** | The required table names and the optional table names. ~~Tuple[List[str], List[str]]~~ |
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## Lemmatizer.to_disk {#to_disk tag="method"}
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Serialize the pipe to disk.
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> #### Example
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>
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> ```python
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> lemmatizer = nlp.add_pipe("lemmatizer")
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> lemmatizer.to_disk("/path/to/lemmatizer")
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> ```
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| Name | Description |
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| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------ |
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| `path` | A path to a directory, which will be created if it doesn't exist. Paths may be either strings or `Path`-like objects. ~~Union[str, Path]~~ |
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| _keyword-only_ | |
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| `exclude` | String names of [serialization fields](#serialization-fields) to exclude. ~~Iterable[str]~~ |
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## Lemmatizer.from_disk {#from_disk tag="method"}
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Load the pipe from disk. Modifies the object in place and returns it.
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> #### Example
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>
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> ```python
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> lemmatizer = nlp.add_pipe("lemmatizer")
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> lemmatizer.from_disk("/path/to/lemmatizer")
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> ```
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| Name | Description |
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| -------------- | ----------------------------------------------------------------------------------------------- |
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| `path` | A path to a directory. Paths may be either strings or `Path`-like objects. ~~Union[str, Path]~~ |
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| _keyword-only_ | |
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| `exclude` | String names of [serialization fields](#serialization-fields) to exclude. ~~Iterable[str]~~ |
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| **RETURNS** | The modified `Lemmatizer` object. ~~Lemmatizer~~ |
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## Lemmatizer.to_bytes {#to_bytes tag="method"}
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> #### Example
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>
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> ```python
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> lemmatizer = nlp.add_pipe("lemmatizer")
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> lemmatizer_bytes = lemmatizer.to_bytes()
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> ```
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Serialize the pipe to a bytestring.
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| Name | Description |
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| -------------- | ------------------------------------------------------------------------------------------- |
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| _keyword-only_ | |
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| `exclude` | String names of [serialization fields](#serialization-fields) to exclude. ~~Iterable[str]~~ |
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| **RETURNS** | The serialized form of the `Lemmatizer` object. ~~bytes~~ |
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## Lemmatizer.from_bytes {#from_bytes tag="method"}
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Load the pipe from a bytestring. Modifies the object in place and returns it.
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> #### Example
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>
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> ```python
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> lemmatizer_bytes = lemmatizer.to_bytes()
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> lemmatizer = nlp.add_pipe("lemmatizer")
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> lemmatizer.from_bytes(lemmatizer_bytes)
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> ```
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| Name | Description |
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| -------------- | ------------------------------------------------------------------------------------------- |
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| `bytes_data` | The data to load from. ~~bytes~~ |
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| _keyword-only_ | |
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| `exclude` | String names of [serialization fields](#serialization-fields) to exclude. ~~Iterable[str]~~ |
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| **RETURNS** | The `Lemmatizer` object. ~~Lemmatizer~~ |
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## Attributes {#attributes}
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| Name | Description |
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| --------- | ------------------------------------------- |
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| `vocab` | The shared [`Vocab`](/api/vocab). ~~Vocab~~ |
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| `lookups` | The lookups object. ~~Lookups~~ |
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| `mode` | The lemmatizer mode. ~~str~~ |
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## Serialization fields {#serialization-fields}
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During serialization, spaCy will export several data fields used to restore
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different aspects of the object. If needed, you can exclude them from
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serialization by passing in the string names via the `exclude` argument.
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> #### Example
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>
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> ```python
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> data = lemmatizer.to_disk("/path", exclude=["vocab"])
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> ```
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| Name | Description |
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| --------- | ---------------------------------------------------- |
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| `vocab` | The shared [`Vocab`](/api/vocab). |
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| `lookups` | The lookups. You usually don't want to exclude this. |
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