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A dataset generator for Rasa NLU

Project description

Chatette dataset generator

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Chatette is a Python script that helps you generate training datasets for the Rasa NLU Python package. If you want to make large datasets of example data for Natural Language Understanding tasks without too much of a headache, Chatette is a project for you.

Specifically, Chatette implements a Domain Specific Language (DSL) that allows you to define templates to generate a large number of sentences. Those sentences are then saved in the input format of Rasa NLU.

The DSL used is a superset of the excellent project Chatito created by Rodrigo Pimentel. (Note: the DSL is actually a superset of Chatito v2.1.x for Rasa NLU, not for all possible adapters.)

How to use Chatette?

Input and output data

The data that Chatette uses and generates is loaded from and saved to files. We thus have:

  • The input file containing the templates.

    There is no need for a specific file extension. The syntax of the DSL to make those templates is described in the syntax specification. Note that templates can be divided into several files, with one master file linking them all together (described in the syntax specification).

  • The output file, a JSON file containing data that can be directly fed to Rasa NLU.

Running Chatette

To run Chatette, you will need to have Python installed. Chatette works with both Python 2.x and 3.x.

Install Chatette via pip:

pip install chatette

(Alternatively, you can clone the GitHub repository and run the file named

Then simply run the following command:

python -m chatette <path_to_template>


python3 -m chatette <path_to_template>

You can specify the name of the output file as follows:

python -m chatette <path_to_template> -o <output_directory_path>


python3 -m chatette <path_to_template> --output <output_directory_path>

The output file(s) will then be saved in numbered .json files in <output_directory_path>/train and <output_directory_path>/test (<output_directory_path> is specified with respect to the directory from which the script is being executed). If you didn't specify a path for the output directory, the default one is output.

Other program arguments

A bunch of more specific program arguments exist to allow for a more controlled execution of the program. Here is a list of those arguments:

  • -s or --seed followed by any string (without spaces): sets the random generator seed to the string that follows the argument. If you execute Chatette twice with the same seed on the exact same template, the generated output(s) is guaranteed to be exactly the same on both executions.

  • -l or --local: changes the output path to be specified with respect to the directory in which the template file is, rather than the current working directory.

  • -a or --adapter: changes which adapter will be used to write the output (defaults to the Rasa NLU adapter). Currently, two adapters exist: one to produce files that can be used as input to Rasa NLU and one that makes .jsonl files containing JSON representations of the examples. The possible values for this arguments are thus rasa or jsonl.

Chatette vs Chatito?

A perfectly legitimate question could be:

Why does Chatette exist when Chatito already fulfills the same purposes?

The reason comes from the different goals of the two projects:

Chatito aims at a generic but powerful DSL, that should stay simple. While it is perfectly fine for small projects, when projects get larger, this simplicity may become a burden: your template file becomes overwhelmingly large, at a point you get lost inside it.

Chatette defines a more complex DSL to be able to manage larger projects. Here is a non-exhaustive list of features that can help with that:

  • Ability to break down templates into multiple files
  • Support for comments inside template files (Note: this is now possible in Chatito v2.1.x too)
  • Word group syntax that allows to define parts of sentences that might not be generated in every example
  • Possibility to specify the probability of generating some parts of the sentences
  • Choice syntax to prevent copy-pasting rules with only a few changes
  • Ability to define the value of each slot whatever the generated example
  • Syntax for generating words with different case for the leading letter
  • Argument support so that some templates may be filled by given words
  • Indentation must simply be somewhat coherent
  • Support for synonyms

As previously mentioned, the DSL used by Chatette is a superset of the one used by Chatito. This means that input files used for Chatito are completely usable with Chatette (not the other way around). Hence, it is easy to get from Chatito to Chatette.

As an example, this Chatito data:

// This template defines different ways to ask for the location of toilets (Chatito version)
%[ask_toilet]('training': '3')
    ~[sorry?] ~[tell me] where the @[toilet#singular] is ~[please?]?
    ~[sorry?] ~[tell me] where the @[toilet#plural] are ~[please?]?

    excuse me
    Excuse me

~[tell me]
    ~[can you?] tell me
    ~[can you?] show me
~[can you]
    can you
    could you
    would you



could be directly given as input to Chatette, but this Chatette template would produce the same thing:

// This template defines different ways to ask for the location of toilets (Chatette version)
    ~[sorry?] ~[tell me] where the {@[toilet#singular] is/@[toilet#plural] are} [please?]\?

    excuse me

~[tell me]
    ~[can you?] {tell/show} me
~[can you]
    {can/could/would} you


The Chatito version is arguably easier to read, but the Chatette version is shorter, which may be very useful when dealing with lots of templates and potential repetition.

Beware that, as always with machine learning, having too much data may cause your models to perform less well because of overfitting. While this script can be used to generate thousands upon thousands of examples, it isn't advised for machine learning tasks.

Note that Chatette is named after Chatito, as -ette in French could be translated to -ita or -ito in Spanish.


Install development requirements:

pip install -r requirements/develop.txt

Run pylint:

tox -e pylint

Run pycodestyle:

tox -e pycodestyle

Run pytest:

tox -e pytest


Author and maintainer

Disclaimer: This is a side-project I'm not paid for, don't expect me to work 24/7 on it.


Many thanks to him!

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