# Config Commands¶

This page explains the usage of the commands help-config to explore PyText components, and gen-default-config to create a config file with custom components and parameters.

## Exploring Config Options¶

You can explore PyText Components with the command help-config. This will print the documentation of the component, its full module name, its base class, as well as the list of its config parameters, their type and their default value.

$pytext help-config LMTask === pytext.task.tasks.LMTask (NewTask) === data = Data exporter = null features = FeatureConfig featurizer = SimpleFeaturizer metric_reporter: LanguageModelMetricReporter = LanguageModelMetricReporter model: LMLSTM = LMLSTM trainer = TaskTrainer  You can drill down to the component you’re interested in. For example, if you want to know more about the model LMLSTM, you can use the same command. Notice how PyText lists the possible values for Union types (for example with representation below.) $ pytext help-config LMLSTM
=== pytext.models.language_models.lmlstm.LMLSTM (BaseModel) ===
"""
LMLSTM implements a word-level language model that uses LSTMs to
represent the document.
"""
ModelInput = LMLSTM.Config.ModelInput
caffe2_format: (ExporterType)
PREDICTOR (default)
INIT_PREDICT
decoder: (one of)
None
MLPDecoder (default)
embedding: WordFeatConfig = WordEmbedding
inputs: LMLSTM.Config.ModelInput = ModelInput
output_layer: LMOutputLayer = LMOutputLayer
representation: (one of)
DeepCNNRepresentation
BiLSTM (default)
stateful: bool
tied_weights: bool


PyText internally registers all the component classes, so we can look up and find any component using the class name or their aliases. For example somewhere in PyText we have import DeepCNNRepresentation as CNN, so we would normally look up DeepCNNRepresentation, but if we know that this class has an alias we can look up CNN instead, and print the information about this class:

$pytext help-config CNN === pytext.models.representations.deepcnn.DeepCNNRepresentation (RepresentationBase) === """ DeepCNNRepresentation implements CNN representation layer preceded by a dropout layer. CNN representation layer is based on the encoder in the architecture proposed by Gehring et. al. in Convolutional Sequence to Sequence Learning. Args: config (Config): Configuration object of type DeepCNNRepresentation.Config. embed_dim (int): The number of expected features in the input. """ cnn: CNNParams = CNNParams dropout: float = 0.3  ## Creating a Config File¶ The command gen-default-config creates a json config files for a given Task using the default value for all the parameters. You must specify the class name of the Task. The json config will be printed in the terminal, so you need to send it to a file using of your choice (for example my_config.json) to be able to edit it and use it. $ pytext gen-default-config LMTask > my_config.json
...


In the help-config LMLSTM above, we see that representation is by default BiLSTM, but could also be DeepCNNRepresentation. (This can be because the type is declared as a Union of valid alternatives, or because the type is a base class.) Those two classes will have different parameters, so we can’t just edit the my_config.json and replace the class name.

We can specify which components to use by adding any number of class names to the command. Let’s create this config, and we’ll use add DeepCNNRepresentation to our command. gen-default-config will look up this class name and find that it is a suitable representation component for the LMLSTM model in our LMTask.

$pytext gen-default-config LMTask DeepCNNRepresentation > my_config.json INFO - Applying task option: LMTask INFO - Applying class option: task->model->representation = CNN ...  This also works with parameters which are not component class names. You can specify the parameter name and its value, and gen-default-config will automatically apply this parameter to the right component. $ pytext gen-default-config LMTask epochs=200
INFO - Applying parameter option to task.trainer.epochs : epochs=200
...


Sometimes the same parameter name is used by multiple components. In this case PyText prints the list of those parameters with their full config path. You can then simply use the last part of the path that is enough to differentiate them and pick the one you want. In the next example, we omit the prefix task.model. because we don’t need it to find where to apply our parameter representation.dropout.

$pytext gen-default-config LMTask dropout=0.7 > my_config.json INFO - Applying task option: LMTask ... Exception: Multiple possibilities for dropout=0.7: task.model.representation.dropout, task.model.decoder.dropout$ pytext gen-default-config LMTask representation.dropout=0.7 > my_config.json
INFO - Applying parameter option to task.model.representation.dropout : representation.dropout=0.7
...


You can add any number and combination of those parameters. Please note that they will be applied in order, so if you want to change a component class and some of its parameters, you must specify the parameters in this order (component first, then parameters). If you don’t do that, your parameters changes will be ignored. For example, changing representation.dropout first, then overriding the representation component will replace the default representation with a new CNN component with all the parameter using the default value.

Look at this bad example: you can verify that the representation dropout is 0.3 (the default value for CNN) and not 0.7 as we specified, because CNN was applied after and replaced the component that had its dropout modified first.

$pytext gen-default-config LMTask representation.dropout=0.7 CNN > my_config.json INFO - Applying task option: LMTask INFO - Applying parameter option to task.model.representation.dropout : representation.dropout=0.7 INFO - Applying class option: task->model->representation = CNN ...  Now let’s combine everything: $ pytext gen-default-config LMTask BlockShardedTSVDataSource CNN dilated=True epochs=200 representation.dropout=0.7 > my_config.json
INFO - Applying class option: task->data->source = BlockShardedTSVDataSource
INFO - Applying class option: task->model->representation = CNN
INFO - Applying parameter option to task.model.representation.cnn.dilated : dilated=True
INFO - Applying parameter option to task.trainer.epochs : epochs=200
INFO - Applying parameter option to task.model.representation.dropout : representation.dropout=0.2
...


## Updating a Config File¶

When there’s a new release of PyText, some component parameters might change because of bug fixes or new features. While PyText has config_adapters that can internally transform old configs to map them to the latest components, it is sometimes useful to update your config file to the current version. This can be done with the command update-config:

\$ pytext update-config < my_config_old.json > my_config_new.json