By David Bieber, Software Engineer on
Google Brain
Today we are pleased to announce the open-sourcing of
Python Fire. Python Fire generates command line interfaces (CLIs)
from any Python code. Simply call the Fire function in any Python program to automatically
turn that program into a CLI. The library is available from pypi via `pip install fire`, and the source is available on
GitHub.
Python Fire will automatically turn your code into a CLI without you needing to
do any additional work. You don't have to define arguments, set up help information, or write
a main function that defines how your code is run. Instead, you simply call the `Fire`
function from your main module, and Python Fire takes care of the rest. It uses inspection to
turn whatever Python object you give it -- whether it's a class, an object, a dictionary, a
function, or even a whole module -- into a command line interface, complete with tab
completion and documentation, and the CLI will stay up-to-date even as the code
changes.
To illustrate this, let's look at a simple example.
#!/usr/bin/env python
import fire
class Example(object):
def
hello(self, name='world'):
"""Says hello to
the specified name."""
return 'Hello {name}!'.format(name=name)
def main():
fire.Fire(Example)
if __name__ == '__main__':
main()
When the Fire function is run, our command will be executed. Just by calling
Fire, we can now use the Example class as if it were a command line utility.
$ ./example.py hello
Hello world!
$ ./example.py hello David
Hello David!
$ ./example.py hello --name=Google
Hello Google!
Of course, you can continue to use this module like an ordinary Python library,
enabling you to use the exact same code both from Bash and Python. If you're writing a Python
library, then you no longer need to update your main method or client when experimenting with
it; instead you can simply run the piece of your library that you're experimenting with from
the command line. Even as the library changes, the command line tool stays up to
date.
At Google, engineers use Python Fire to generate command
line tools from Python libraries. We have an image manipulation tool built by using Fire with
the Python Imaging Library, PIL. In
Google Brain, we use an experiment management tool
built with Fire, allowing us to manage experiments equally well from Python or from
Bash.
Every Fire CLI comes with an interactive mode. Run the
CLI with the `--interactive` flag to launch an IPython
REPL with the result
of your command, as well as other useful variables already defined and ready to use. Be sure
to check out Python Fire's
documentation for more on this and the other useful features Fire
provides.
Between Python Fire's simplicity, generality, and power, we hope you find it a
useful library for your own projects.
