detect pip in setup.py

Question

Gist: What is the best way to detect in setup.py that we are being triggered by pip install package?

Background: I have a package (bindings for a C-library), for which I provide eggs that include the library itself. In my readme/docs I note that this package is 'easy_install-able' on certain platforms. When building from source (e.g. with pip), the library itself is a build dependency. The problem is that I somewhat regularly have confused users who mistakenly believe that pip is a full replacement for easy_install, and expect pip install package to work on systems without the library, or even without a compiler, where the egg is what they really want.

I would like to detect that the build has been triggered by pip, so I can provide a friendly "pip != easy_install" message if it fails due to lacking the library. It doesn't need to be perfect, just catch the most common cases of pip install package. On inspection, it doesn't seem like there is a particularly robust way to do this, and the best I have come up with is:

probably_using_pip = '--single-version-externally-managed' in sys.argv

Is there a better (or better yet, official) way to detect pip from setup.py?

Answer 1

__file__ in setup gives something like /tmp/pip-DNpsLw-build/setup.py if ran from pip.

from setuptools import setup

def determineInstaller():
    if 'pip' in __file__:
        print('========pip triggered build========') #add smiley for friendliness :)
    return 'dummy description'

setup(name='bla',
      version='0.0',
      description=determineInstaller(),
      )