virtualenv.py 文件源码

def _activate_env_from_path(env_path):
    """ Fix when `activate_this.py` does not exist.

        For Python 3.3 and newer, a new command-line tool `pyvenv` create venv
        will not provide 'activate_this.py'.
    """
    prev_sys_path = list(sys.path)

    if sys.platform == 'win32':
        site_packages_paths = [os.path.join(env_path, 'Lib', 'site-packages')]
    else:
        lib_path = os.path.join(env_path, 'lib')
        site_packages_paths = [os.path.join(lib_path, lib, 'site-packages')
                               for lib in os.listdir(lib_path)]
    for site_packages_path in site_packages_paths:
        site.addsitedir(site_packages_path)

    sys.real_prefix = sys.prefix
    sys.prefix = env_path
    sys.exec_prefix = env_path

    # Move the added items to the front of the path:
    new_sys_path = []
    for item in list(sys.path):
        if item not in prev_sys_path:
            new_sys_path.append(item)
            sys.path.remove(item)
    sys.path[:0] = new_sys_path