How to specify install order for python pip?

You can just use:

cat requirements.txt | xargs pip install

To allow all types of entries (for example packages from git repositories) in requirements.txt you need to use the following set of commands

cat requirements.txt | xargs -n 1 -L 1 pip install

-n 1 and -L 1 options are necessary to install packages one by one and treat every line in the requirements.txt file as a separate item.

This is a silly hack, but might just work. Write a bash script that reads from your requirements file line by line and runs the pip command on it.

#!/bin/bash
for line in $(cat requirements.txt)
do
  pip install $line -E /path/to/virtualenv
done