Command Line Interface: fire

Python Fire is a library for automatically generating command-line interfaces (CLIs) from absolutely any Python object.

Python Fire is a simple way to create a CLI in Python.
Python Fire is a helpful tool for developing and debugging Python code.
Python Fire helps with exploring existing code or turning other people’s code into a CLI.
Python Fire makes transitioning between Bash and Python easier.
Python Fire makes using a Python REPL easier by setting up the REPL with the modules and variables you’ll need already imported and created.

For more information visit https://google.github.io/python-fire/

Installation

$ poetry add fire

Basic Usage

You can call Fire on any Python object: functions, classes, modules, objects, dictionaries, lists, tuples, etc. They all work!

Here’s an example of calling Fire on a function.

from numbers import Real

import fire

def add(a: Real, b: Real) -> Real:
    return a + b

if __name__ == '__main__':
    fire.Fire(add)

Then, from the command line, you can run:

$ python -m python_lifecycle_training.calculator.simple 2 2
4

Now, let us try calling Fire on a class by creating a complex calculator.

# python_lifecycle_training/calculator/complex.py
import fire


class Calculator:
    @staticmethod
    def add(a, b):
        return a + b

    @staticmethod
    def sub(a, b):
        return a - b

    @staticmethod
    def mul(a, b):
        return a * b

    @staticmethod
    def div(a, b):
        return a / b


if __name__ == "__main__":
    fire.Fire(Calculator)

Then, from the command line, you can run:

$ python -m python_lifecycle_training.calculator.complex add 2 2
4

$ python -m python_lifecycle_training.calculator.complex sub 2 2
0

$ python -m python_lifecycle_training.calculator.complex mul 2 2
4

$ python -m python_lifecycle_training.calculator.complex div 2 2
1.0

Self-defined Commands

It is pretty tedious to run our commands like this so let us create some entry points. First replace the file executable if __name__ == "__main__": with a main method that calls your fire command.

Before

if __name__ == "__main__":
    fire.Fire(Calculator)

After

def main():
    fire.Fire(Calculator)

Now create entry points in pyproject.toml below dev-dependencies.

[tool.poetry.scripts]
calc-simp = "python_lifecycle_training.calculator.simple:main"
calc-complex = "python_lifecycle_training.calculator.complex:main"

Install your package via poetry

$ poetry install

Now you can run:

$ calc-simp 2 2
4

$ calc-complex add 2 2
4

Note

Comment out disallow_untyped_defs = true for mypy in setup.cfg for convenience

Next Step

To move on to the next step commit or stash your changes then checkout to the branch setup/log/loguru

$ git stash
$ git checkout setup/log/loguru

Uninstall

$ poetry remove fire