Script to link Python system package into virtual environment from Nick Coghlan at https://bitbucket.org/ncoghlan/misc/raw/44341af0b2e4ac7f9580d5f907d8f49c7013b3b9/venv_link.py Modified to use system python to find the module, and pip to decide the link location

venv_link.py

#!/usr/bin/env python
# symlink a system package or module into the current virtual env

import logging
import optparse
import os
import sys
import shutil
import subprocess
import pickle
import pip.locations

pyver_str = "%d.%d" % sys.version_info[:2]

def find_sys_python():
    return "/usr/bin/python%s" % pyver_str

def sys_python_find_module(python_exe, name):
    cmd = "import imp, pickle, sys ; f, real_path, mod_info = imp.find_module('%s') ; f and f.close() ; pickle.dump((real_path, mod_info), sys.stdout)" % name
    p = subprocess.check_output([python_exe, "-c", cmd])
    t = pickle.loads(p)
    real_path, mod_info = t
    return real_path, mod_info

def find_files(base, dir_name):
    file_list = []
    for file_name in os.listdir(os.path.join(base, dir_name)):
        file_list.append(os.path.join(dir_name, file_name))
        if os.path.isdir(os.path.join(base, dir_name, file_name)):
           file_list.extend(find_files(base, os.path.join(dir_name, file_name)))
    return file_list

def confirm_remove(target_path):
    """removes the given target path after obtaining user confirmation"""
    remove = raw_input("Target %s already exists - remove? (yes/no) " % target_path).lower() == "yes"
    if remove:
        if os.path.isdir(target_path) and not os.path.islink(target_path):
            shutil.rmtree(target_path)
        else:
            os.remove(target_path)

def install_link(names, action=None, egg_info=None, egg_version=None, sys_python=None):
    """'Install' a module or package by linking to system version"""

    virt_prefix = sys.prefix
    real_prefix = getattr(sys, "real_prefix", None)
    if real_prefix is None or real_prefix == virt_prefix:
        raise Exception("Not in a virtual environment")

    virt_dir = pip.locations.site_packages
    installed_files = []
    python_exe = find_sys_python() if sys_python is None else sys_python

    for name in names:
        # We want to see what the system Python would import...
        real_path, mod_info = sys_python_find_module(python_exe, name)

        mod_suffix, fmode, mod_type = mod_info
        file_name = os.path.basename(real_path)
        target_path = os.path.join(virt_dir, file_name)

        if os.path.exists(target_path):
            confirm_remove(target_path)
        if action == "link":
            print "{} -> {}".format(target_path, real_path)
            os.symlink(real_path, target_path)
        elif action == "copy":
            print "copying {} -> {}".format(real_path, target_path)
            if os.path.isdir(real_path):
                shutil.copytree(real_path, target_path)
                tree_files = find_files(virt_dir, file_name)
                installed_files.extend([os.path.join("..", file_name) for file_name in tree_files])
            else:
                shutil.copy2(real_path, target_path)
                installed_files.append(os.path.join("..", file_name))
    if egg_info:
        if action == "link":
            logging.warning("Linked files will not be listed under egg_info as pip uninstall attempts to remove the targets rather than the links")
        egg_info_dir = os.path.join(virt_dir, "%s-%s.egg-info" % (egg_info, egg_version if egg_version else "py%s" % pyver_str))
        if os.path.exists(egg_info_dir):
            confirm_remove(egg_info_dir)
        print "creating {}".format(egg_info_dir)
        os.mkdir(egg_info_dir)
        installed_lines = [installed_file + "\n" for installed_file in installed_files]
        with open(os.path.join(egg_info_dir, 'installed-files.txt'), 'w') as f:
            f.writelines(installed_lines)
        if egg_version:
            with open(os.path.join(egg_info_dir, 'PKG-INFO'), 'w') as f:
                f.writelines(["Metadata-Version: 1.1\n", "Name: %s\n" % egg_info, "Version: %s\n" % egg_version])

if __name__ == "__main__":
    parser = optparse.OptionParser()
    parser.add_option("-e", "--egg-info", dest="egg_info", help="Create egg-info entry for the given package name", default=None)
    parser.add_option("-v", "--egg-version", dest="egg_version", help="Set the version of the egg info to this", default=None)
    parser.add_option("-p", "--python", dest="sys_python", help="Use the given python executable as source for the modules", default=None)
    parser.add_option("-c", "--copy", dest="action", action="store_const", const="copy", help="Copy modules into virtualenv (default)", default="copy")
    parser.add_option("-l", "--link", dest="action", action="store_const", const="link", help="Link to modules rather than copying")
    options, names = parser.parse_args()
    install_link(names, action=options.action, egg_info=options.egg_info, egg_version=options.egg_version, sys_python=options.sys_python)