The Python Fire shebang

Happy valentine’s day! Today’s snippet is about a feature of Python Fire, new in v0.4.0, and how you can use it to create Python Fire executables just by adding a shebang to an existing Python file. This idea is courtesy of c6401 in GitHub issue #319. The shebang line is #!/usr/bin/env -S python3 -m fire.

The feature introduced in fire v0.4.0 is that python -m fire now accepts filepaths.

Suppose you have a Python file at path/to/module.py. Previously, you could invoke module.py as a Fire CLI with the command python -m fire path.to.module. That still works, but now you can also use the command python -m fire path/to/module.py. This is roughly equivalent to running module.py and then calling fire.Fire() as the final line of the module.

A consequence of this new feature is that the shebang #!/usr/bin/env -S python3 -m fire allows you to create executable CLIs out of Python files. /usr/bin/env -S is explained here. To create a Python Fire executable, simply add the shebang line as the first line of the file, and then use chmod +x to mark the file as executable.

Here’s a quick example:

Save it as e.g. shebang.py, run chmod +x shebang.py to make it executable, and run it with ./shebang.py hello --name=David

> ./shebang.py hello --name=David
Hello David!

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