What is setup.py?

Question

Can anyone please explain what setup.py is and how it can be configured or used?

Answer 1

To install a Python package you've downloaded, you extract the archive and run the setup.py script inside:

python setup.py install

To me, this has always felt odd. It would be more natural to point a package manager at the download, as one would do in Ruby and Nodejs, eg. gem install rails-4.1.1.gem

A package manager is more comfortable too, because it's familiar and reliable. On the other hand, each setup.py is novel, because it's specific to the package. It demands faith in convention "I trust this setup.py takes the same commands as others I have used in the past". That's a regrettable tax on mental willpower.

I'm not saying the setup.py workflow is less secure than a package manager (I understand Pip just runs the setup.py inside), but certainly I feel it's awkard and jarring. There's a harmony to commands all being to the same package manager application. You might even grow fond it.