pip requirements.txt with alternative index

requirements.txt:

-i http://dist.repoze.org/zope2/2.10/simple
zopelib

Example:

$ pip install -r requirements.txt
...
Successfully installed zopelib

Add an extra index location to the requirements file just before the package/project name:

--extra-index-url <Extra URLs other than index-url>
<some_project_name>

Alternatively, you may use -i or --index-url <Base URL of the Python Package Index>.

Refer: requirements file format