Ensure venv is first in the path

modify_path.py

#! /usr/bin/python

import argparse
import os
import sys


PREPEND = 'prepend'
APPEND = 'append'
SEP = ':'


def main(args=None):
    parser = argparse.ArgumentParser()
    parser.add_argument('where', choices=(PREPEND, APPEND))
    parser.add_argument('items')
    args = parser.parse_args(args)

    items = []
    for item in args.items.split(SEP):
        item = os.path.abspath(item)
        if not os.path.isdir(item):
            raise Exception('{} does not exists'.format(item))
        items.append(item)

    path = os.environ['PATH']
    path = path.split(SEP)

    output_path = []

    # ensure that the virtual environmen is at the front
    venv = os.environ.get('VIRTUAL_ENV')
    if venv:
        output_path.append(os.path.join(venv, 'bin'))

    if args.where == PREPEND:
        output_path.extend(items)

    for item in path:
        if item not in output_path:
            output_path.append(item)

    if args.where == APPEND:
        output_path.extend(items)

    print(SEP.join(output_path))


if __name__ == '__main__':
    sys.exit(main())

Can be used in .bashrc to modify path. Its needed because the venv path should always be first, but any prepend actions in bashrc will add to the path. venv's also end up with lots of duplicate paths, this cleans them up