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			278 lines
		
	
	
		
			15 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_base_class: /api/pipe
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| api_string_name: lemmatizer
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| api_trainable: false
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| ---
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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. Functionality to train the component is coming soon.
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| Different [`Language`](/api/language) subclasses can implement their own
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| 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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| 
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| <Infobox variant="warning" title="New in v3.0">
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| 
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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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| 
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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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| 
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| </Infobox>
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| 
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| ## Config and implementation
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| 
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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 formats 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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| 
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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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| 
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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"`. ~~str~~                                                                                                                                                                                                   |
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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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| | `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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| 
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| ```python
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| %%GITHUB_SPACY/spacy/pipeline/lemmatizer.py
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| ```
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| 
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| ## Lemmatizer.\_\_init\_\_ {#init tag="method"}
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| 
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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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| 
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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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| 
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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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| | lookups        | A lookups object containing the tables such as `"lemma_rules"`, `"lemma_index"`, `"lemma_exc"` and `"lemma_lookup"`. Defaults to `None`. ~~Optional[Lookups]~~ |
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| | overwrite      | Whether to overwrite existing lemmas. ~~bool~                                                                                                                  |
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| 
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| ## Lemmatizer.\_\_call\_\_ {#call tag="method"}
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| 
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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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| 
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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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| 
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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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| 
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| ## Lemmatizer.pipe {#pipe tag="method"}
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| 
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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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| 
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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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| 
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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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| 
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| ## Lemmatizer.lookup_lemmatize {#lookup_lemmatize tag="method"}
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| 
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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. Languages can provide a
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| [lookup table](/usage/adding-languages#lemmatizer) via the `Lookups`.
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| 
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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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| 
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| ## Lemmatizer.rule_lemmatize {#rule_lemmatize tag="method"}
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| 
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| Lemmatize a token using a rule-based approach. Typically relies on POS tags.
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| 
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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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| 
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| ## Lemmatizer.is_base_form {#is_base_form tag="method"}
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| 
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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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| 
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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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| 
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| ## Lemmatizer.get_lookups_config {#get_lookups_config tag="classmethod"}
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| 
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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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| 
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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 lookups configuration settings for this mode. Includes the keys `"required_tables"` and `"optional_tables"`, mapped to a list of table string names. ~~Dict[str, List[str]]~~ |
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| 
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| ## Lemmatizer.load_lookups {#load_lookups tag="classmethod"}
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| 
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| Load and validate lookups tables. If the provided lookups is `None`, load the
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| default lookups tables according to the language and mode settings. Confirm that
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| all required tables for the language and mode are present.
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| 
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| | Name        | Description                                                                                        |
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| | ----------- | -------------------------------------------------------------------------------------------------- |
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| | `lang`      | The language. ~~str~~                                                                              |
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| | `mode`      | The lemmatizer mode. ~~str~~                                                                       |
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| | `lookups`   | The provided lookups, may be `None` if the default lookups should be loaded. ~~Optional[Lookups]~~ |
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| | **RETURNS** | The lookups. ~~Lookups~~                                                                           |
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| 
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| ## Lemmatizer.to_disk {#to_disk tag="method"}
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| 
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| Serialize the pipe to disk.
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| 
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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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| 
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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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| 
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| ## Lemmatizer.from_disk {#from_disk tag="method"}
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| 
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| Load the pipe from disk. Modifies the object in place and returns it.
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| 
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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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| 
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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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| 
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| ## Lemmatizer.to_bytes {#to_bytes tag="method"}
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| 
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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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| 
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| Serialize the pipe to a bytestring.
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| 
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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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| 
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| ## Lemmatizer.from_bytes {#from_bytes tag="method"}
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| 
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| Load the pipe from a bytestring. Modifies the object in place and returns it.
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| 
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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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| 
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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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| 
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| ## Attributes {#attributes}
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| 
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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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| 
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| ## Serialization fields {#serialization-fields}
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| 
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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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| 
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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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| 
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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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