To make it simple, setup.py is run as "__main__"
when you call the install functions the other answers mentioned. Inside setup.py, you should put everything needed to install your package.
The following two sections discuss two things many setup.py modules have.
This function allows you to specify project attributes like the name of the project, the version.... Most importantly, this function allows you to install other functions if they're packaged properly. See this webpage for an example of setuptools.setup
These attributes of setuptools.setup enable installing these types of packages:
Packages that are imported to your project and listed in PyPI using setuptools.findpackages:
packages=find_packages(exclude=["docs","tests", ".gitignore", "README.rst","DESCRIPTION.rst"])
Packages not in PyPI, but can be downloaded from a URL using dependency_links
dependency_links=["http://peak.telecommunity.com/snapshots/",]
In an ideal world, setuptools.setup
would handle everything for you. Unfortunately this isn't always the case. Sometimes you have to do specific things, like installing dependencies with the subprocess command, to get the system you're installing on in the right state for your package. Try to avoid this, these functions get confusing and often differ between OS and even distribution.