Import Usage Note

Now there is a very important problem with taking this approach – setupext has to be installed BEFORE setup.py runs. This means that you cannot depend on setup_requires to install the extension. This is very unfortunate and made me consider not releasing this helper at all.

Using Requirement Files

setuptools.setup takes three keyword parameters that control which requirements are installed and when. Here’s what the setuptools documentation has to say about these parameters.


A string or list of strings specifying what other distributions need to be present in order for the setup script to run. setuptools will attempt to obtain these (even going so far as to download them using EasyInstall) before processing the rest of the setup script or commands. This argument is needed if you are using distutils extensions as part of your build process; for example, extensions that process setup() arguments and turn them into EGG-INFO metadata files.

(Note: projects listed in setup_requires will NOT be automatically installed on the system where the setup script is being run. They are simply downloaded to the setup directory if they’re not locally available already. If you want them to be installed, as well as being available when the setup script is run, you should add them to install_requires and setup_requires.)


If your project’s tests need one or more additional packages besides those needed to install it, you can use this option to specify them. It should be a string or list of strings specifying what other distributions need to be present for the package’s tests to run. When you run the test command, setuptools will attempt to obtain these (even going so far as to download them using EasyInstall). Note that these required projects will not be installed on the system where the tests are run, but only downloaded to the project’s setup directory if they’re not already installed locally.


A dictionary mapping names of “extras” (optional features of your project) to strings or lists of strings specifying what other distributions must be installed to support those features. See the section below on Declaring Dependencies for details and examples of the format of this argument.

You can use read_requirements_from_file() to read each set of dependencies from a separate file. This practice makes it possible to organize simple or complex dependencies in a DRY manner.

import setuptools
from setupext import pip

    # ...

Now back to the ominous warning above. If you can’t guarantee that the extension is installed into the environment that your package is installed into, then you can roll your own implementation of reading the requirements file. I’ve used the following snippet to work through this problem with, admittedly, simple requirements files.

    from setupext.pip import read_requirements_from_file
except ImportError:
    def read_requirements_from_file(req_name):
        with open(req_name, 'r') as req_file:
            return [
                line[0:line.find('#')] if '#' in line else line.strip()
                for line in req_file

It’s no where near perfect, but it does work in most cases.


Read requirements from a pip-formatted requirements file.

Parameters:file_name (str) – the name of the file to read from
Returns:a list of requirements as strings

This function reads the specified file, processes it as the pip utility would, and returns the list of dependency specifiers. Each line of the requirements file is parsed using the functionality provided by pkg_resources so even the hairiest dependency specifiers will be parsed correctly. However, all command line parameter overrides (e.g., --index-file=...) are ignored.