Editing Python Project Dependencies (section)

== setup.py ==

In addition to `requirements.txt`, `setup.py` is another file used to check for dependencies when installing a package. <ref>[https://caremad.io/posts/2013/07/setup-vs-requirement/ setup.py vs requirements.txt], Donald Stufft</ref>

`setup.py` defines ''abstract'' dependencies for redistributable packages. The specific ''source'' for those dependencies should be defined elsewhere, e.g. `requirements.txt`. 

Given a directiory containing a `setup.py` file, a `requirements.txt` file can be written that will install all dependencies found in `setup.py` from PyPi: 

<pre>
--index-url https://pypi.python.org/simple

-e .
</pre>

If any dependencies should come from another source, `requirements.txt` can be modified similar to this:

<pre>
--index-url https://pypi.python.org/simple

-e https://github.com/foo/bar.git#egg=bar
-e .
</pre>

`pip` will first install the `bar` library from GitHub, then move on to install all the dependencies found in `setup.py`. Since the `bar` library has already been installed at this point, it will be skipped over when installing libraries from PyPi.

=== Installing packages defined in setup.py ===

Command to install the project dependencies defined in `setup.py`: <ref>[https://stackoverflow.com/questions/1471994/what-is-setup-py What is setup.py] - Stackoverflow</ref> <ref>[https://docs.python.org/3/installing/index.html#installing-index Installing Python Modules] - Python Software Foundation</ref>

<syntaxhighlight lang="bash">
$ python setup.py install
</syntaxhighlight>