Custom pip index per virtualenv (using virtualenvwrapper)

postactivate

#!/bin/bash
# This hook is sourced after every virtualenv is activated.
# This belongs in $WORKON_HOME/postactivate

VIRTUAL_ENV_NAME=${VIRTUAL_ENV##*/}
if [[ $VIRTUAL_ENV_NAME == *"custom_prefix_"* ]]
then
    export PIP_INDEX_URL="https://pypi.python.org/simple"
else
    # Put this line in postdeactivate as well
    unset PIP_INDEX_URL
fi

postdeactivate

#!/bin/bash
# This hook is sourced after every virtualenv is deactivated.

unset PIP_INDEX_URL