Google Fire: module for CLI and code exploration

While looking at some frameworks to write a CLI in Python, I ran into Google Fire (I hope it’s no a pun on Amazon’s Fire ). It is a clever way to interface almost any Python code.

Basics

Say you have a simple function

def hello(name):
    return 'Hello {name}!'.format(name=name)

Import the module and add a call to Fire at the end, and you have a CLI:

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

It will not do much when you run it. Instead it will display information on how to use it.

$ python3 test1.py
NAME
    test1.py

SYNOPSIS
    test1.py GROUP | COMMAND

GROUPS
    GROUP is one of the following:

     fire
       The Python Fire module.

COMMANDS
    COMMAND is one of the following:

     hello

Now you know there is 1 valid command (the function hello). So to call it, we specify an argument with that name, and any arguments the function expects.

$ python3 test1.py hello Universe
Hello Universe!

That seemed more complex than what I want. After all, now I need to pass an extra argument when I call my script. You can avoid that, by modifying the call to Fire to be:

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

Now Fire passes all arguments directly to that function.

$ python3 test1.py Ocean
Hello Ocean!

More

But this model is very extensible when we have more than 1 function. On top of that it also works with classes and modules. For example:

import fire

"""A test of Fire with a class Object"""


class Calculator(object):
    """A simple calculator class."""

    def add(self, number1, number2):
        """Add two numbers together"""
        return number1 + number2

    def multiple(self, number1, number2):
        """Multiply two numbers together"""
        return number1 * number2


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

And then, you can use it like:

$ python3 test2.py add 2.04 1.1
3.14

Oh, and it reads Python docstrings to get you proper help.

$ python3 test2.py
NAME
    test2.py - A simple calculator class.

SYNOPSIS
    test2.py COMMAND

DESCRIPTION
    A simple calculator class.

COMMANDS
    COMMAND is one of the following:

     add
       Add two numbers together

     multiple
       Multiply two numbers together