Specifying Dependencies

If you’re using Python, odds are you’re going to want to use other public packages from PyPI or elsewhere.

Fortunately, setuptools makes it easy for us to specify those dependencies (assuming they are packaged correctly) and automatically install them when our packages is installed.

We can add some formatting spice to the funniest joke with Markdown.

In text.py:

from markdown import markdown

def joke():
    return markdown(u'Wenn ist das Nunst\u00fcck git und Slotermeyer?'
                    u'Ja! ... **Beiherhund** das Oder die Flipperwaldt '

Now our package depends on the markdown package. To note that in setup.py, we just add an install_requires keyword argument:

from setuptools import setup

      description='The funniest joke in the world',
      author='Flying Circus',

To prove this works, we can run python setup.py develop again, and we’ll see:

$ python setup.py develop
running develop
running egg_info
writing requirements to funniest.egg-info/requires.txt
writing funniest.egg-info/PKG-INFO
writing top-level names to funniest.egg-info/top_level.txt
writing dependency_links to funniest.egg-info/dependency_links.txt
reading manifest file 'funniest.egg-info/SOURCES.txt'
writing manifest file 'funniest.egg-info/SOURCES.txt'
running build_ext
Creating /.../site-packages/funniest.egg-link (link to .)
funniest 0.1 is already the active version in easy-install.pth

Installed /Users/scott/local/funniest
Processing dependencies for funniest==0.1
Searching for Markdown==2.1.1
Best match: Markdown 2.1.1
Adding Markdown 2.1.1 to easy-install.pth file

Using /.../site-packages
Finished processing dependencies for funniest==0.1

When we publish this to PyPI, calling pip install funniest or similar will also install markdown.

Packages Not On PyPI

Sometimes you’ll want to use packages that are properly arranged with setuptools, but aren’t published to PyPI. In those cases, you can specify a list of one or more dependency_links URLs where the package can be downloaded, along with some additional hints, and setuptools will find and install the package correctly.

For example, if a library is published on GitHub, you can specify it like: