# Custom NLU Components [¶](https://legacy-docs-v1.rasa.com/1.5.3/api/custom-nlu-components/#custom-nlu-components "Permalink to this headline")
You can create a custom component to perform a specific task which NLU doesn’t currently offer (for example, sentiment analysis). Below is the specification of the [`rasa.nlu.components.Component`](https://legacy-docs-v1.rasa.com/1.5.3/api/custom-nlu-components/#rasa.nlu.components.Component "rasa.nlu.components.Component") class with the methods you’ll need to implement.
Note
There is a detailed tutorial on building custom components [here](https://blog.rasa.com/enhancing-rasa-nlu-with-custom-components/).
You can add a custom component to your pipeline by adding the module path. So if you have a module called `sentiment` containing a `SentimentAnalyzer` class:
> ```
> pipeline:
> - name: "sentiment.SentimentAnalyzer"
> ```
Also be sure to read the section on the [Component Lifecycle](https://legacy-docs-v1.rasa.com/1.5.3/nlu/choosing-a-pipeline/#section-component-lifecycle).
To get started, you can use this skeleton that contains the most important methods that you should implement:
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| ```
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``` | ````
from rasa.nlu.components import Component
import typing
from typing import Any, Optional, Text, Dict
if typing.TYPE_CHECKING:
from rasa.nlu.model import Metadata
class MyComponent(Component):
"""A new component"""
# Defines what attributes the pipeline component will
# provide when called. The listed attributes
# should be set by the component on the message object
# during test and train, e.g.
# ```message.set("entities", [...])```
provides = []
# Which attributes on a message are required by this
# component. e.g. if requires contains "tokens", than a
# previous component in the pipeline needs to have "tokens"
# within the above described `provides` property.
requires = []
# Defines the default configuration parameters of a component
# these values can be overwritten in the pipeline configuration
# of the model. The component should choose sensible defaults
# and should be able to create reasonable results with the defaults.
defaults = {}
# Defines what language(s) this component can handle.
# This attribute is designed for instance method: `can_handle_language`.
# Default value is None which means it can handle all languages.
# This is an important feature for backwards compatibility of components.
language_list = None
def __init__(self, component_config=None):
super().__init__(component_config)
def train(self, training_data, cfg, **kwargs):
"""Train this component.
This is the components chance to train itself provided
with the training data. The component can rely on
any context attribute to be present, that gets created
by a call to :meth:`components.Component.pipeline_init`
of ANY component and
on any context attributes created by a call to
:meth:`components.Component.train`
of components previous to this one."""
pass
def process(self, message, **kwargs):
"""Process an incoming message.
This is the components chance to process an incoming
message. The component can rely on
any context attribute to be present, that gets created
by a call to :meth:`components.Component.pipeline_init`
of ANY component and
on any context attributes created by a call to
:meth:`components.Component.process`
of components previous to this one."""
pass
def persist(self, file_name: Text, model_dir: Text) -> Optional[Dict[Text, Any]]:
"""Persist this component to disk for future loading."""
pass
@classmethod
def load(
cls,
meta: Dict[Text, Any],
model_dir: Optional[Text] = None,
model_metadata: Optional["Metadata"] = None,
cached_component: Optional["Component"] = None,
**kwargs: Any,
) -> "Component":
"""Load this component from file."""
if cached_component:
return cached_component
else:
return cls(meta)
```` |
## Component [¶](https://legacy-docs-v1.rasa.com/1.5.3/api/custom-nlu-components/#component "Permalink to this headline")
_class_`rasa.nlu.components.``Component`( _component_config=None_) [¶](https://legacy-docs-v1.rasa.com/1.5.3/api/custom-nlu-components/#rasa.nlu.components.Component "Permalink to this definition")
A component is a message processing unit in a pipeline.
Components are collected sequentially in a pipeline. Each component
is called one after another. This holds for
initialization, training, persisting and loading the components.
If a component comes first in a pipeline, its
methods will be called first.
E.g. to process an incoming message, the `process` method of
each component will be called. During the processing
(as well as the training, persisting and initialization)
components can pass information to other components.
The information is passed to other components by providing
attributes to the so called pipeline context. The
pipeline context contains all the information of the previous
components a component can use to do its own
processing. For example, a featurizer component can provide
features that are used by another component down
the pipeline to do intent classification.
_classmethod_`required_packages`() [¶](https://legacy-docs-v1.rasa.com/1.5.3/api/custom-nlu-components/#rasa.nlu.components.Component.required_packages "Permalink to this definition")
Specify which python packages need to be installed.
E.g. `["spacy"]`. More specifically, these should be
importable python package names e.g. sklearn and not package
names in the dependencies sense e.g. scikit-learn
This list of requirements allows us to fail early during training
if a required package is not installed.
Returns
The list of required package names.
Return type
`List`[`str`]
_classmethod_`create`( _component_config_, _config_) [¶](https://legacy-docs-v1.rasa.com/1.5.3/api/custom-nlu-components/#rasa.nlu.components.Component.create "Permalink to this definition")
Creates this component (e.g. before a training is started).
Method can access all configuration parameters.
Parameters
- **component_config** – The components configuration parameters.
- **config** – The model configuration parameters.
Returns
The created component.
Return type
[`Component`](https://legacy-docs-v1.rasa.com/1.5.3/api/custom-nlu-components/#rasa.nlu.components.Component "rasa.nlu.components.Component")
`provide_context`() [¶](https://legacy-docs-v1.rasa.com/1.5.3/api/custom-nlu-components/#rasa.nlu.components.Component.provide_context "Permalink to this definition")
Initialize this component for a new pipeline.
This function will be called before the training
is started and before the first message is processed using
the interpreter. The component gets the opportunity to
add information to the context that is passed through
the pipeline during training and message parsing. Most
components do not need to implement this method.
It’s mostly used to initialize framework environments
like MITIE and spacy
(e.g. loading word vectors for the pipeline).
Returns
The updated component configuration.
Return type
`Optional`[`Dict`[`str`, `Any`]`
`train`( _training_data_, _config=None_, _**kwargs_) [¶](https://legacy-docs-v1.rasa.com/1.5.3/api/custom-nlu-components/#rasa.nlu.components.Component.train "Permalink to this definition")
Train this component.
This is the components chance to train itself provided
with the training data. The component can rely on
any context attribute to be present, that gets created
by a call to [`rasa.nlu.components.Component.create()`](https://legacy-docs-v1.rasa.com/1.5.3/api/custom-nlu-components/#rasa.nlu.components.Component.create "rasa.nlu.components.Component.create")
of ANY component and
on any context attributes created by a call to
[`rasa.nlu.components.Component.train()`](https://legacy-docs-v1.rasa.com/1.5.3/api/custom-nlu-components/#rasa.nlu.components.Component.train "rasa.nlu.components.Component.train")
of components previous to this one.
Parameters
- **training_data** – The `rasa.nlu.training_data.training_data.TrainingData`.
- **config** – The model configuration parameters.
Return type
`None`
`process`( _message_, _**kwargs_) [¶](https://legacy-docs-v1.rasa.com/1.5.3/api/custom-nlu-components/#rasa.nlu.components.Component.process "Permalink to this definition")
Process an incoming message.
This is the components chance to process an incoming
message. The component can rely on
any context attribute to be present, that gets created
by a call to [`rasa.nlu.components.Component.create()`](https://legacy-docs-v1.rasa.com/1.5.3/api/custom-nlu-components/#rasa.nlu.components.Component.create "rasa.nlu.components.Component.create")
of ANY component and
on any context attributes created by a call to
[`rasa.nlu.components.Component.process()`](https://legacy-docs-v1.rasa.com/1.5.3/api/custom-nlu-components/#rasa.nlu.components.Component.process "rasa.nlu.components.Component.process")
of components previous to this one.
Parameters
**message** – The `rasa.nlu.training_data.message.Message` to process.
Return type
`None`
`persist`( _file_name_, _model_dir_) [¶](https://legacy-docs-v1.rasa.com/1.5.3/api/custom-nlu-components/#rasa.nlu.components.Component.persist "Permalink to this definition")
Persist this component to disk for future loading.
Parameters
- **file_name** – The file name of the model.
- **model_dir** – The directory to store the model to.
Returns
An optional dictionary with any information about the stored model.
Return type
`Optional`[`Dict`[`str`, `Any`]`
`prepare_partial_processing`( _pipeline_, _context_) [¶](https://legacy-docs-v1.rasa.com/1.5.3/api/custom-nlu-components/#rasa.nlu.components.Component.prepare_partial_processing "Permalink to this definition")
Sets the pipeline and context used for partial processing.
The pipeline should be a list of components that are
previous to this one in the pipeline and
have already finished their training (and can therefore
be safely used to process messages).
Parameters
- **pipeline** – The list of components.
- **context** – The context of processing.
Return type
`None`
`partially_process`( _message_) [¶](https://legacy-docs-v1.rasa.com/1.5.3/api/custom-nlu-components/#rasa.nlu.components.Component.partially_process "Permalink to this definition")
Allows the component to process messages during
training (e.g. external training data).
The passed message will be processed by all components
previous to this one in the pipeline.
Parameters
**message** – The `rasa.nlu.training_data.message.Message` to process.
Returns
The processed `rasa.nlu.training_data.message.Message`.
Return type
`Message`
_classmethod_`can_handle_language`( _language_) [¶](https://legacy-docs-v1.rasa.com/1.5.3/api/custom-nlu-components/#rasa.nlu.components.Component.can_handle_language "Permalink to this definition")
Check if component supports a specific language.
This method can be overwritten when needed. (e.g. dynamically
determine which language is supported.)
Parameters
**language** – The language to check.
Returns
True if component can handle specific language, False otherwise.
Return type
`bool`