__init__.py 文件源码

def add(path, index=1):
  """Insert site dir or virtualenv at a given index in sys.path.

  Args:
    path: relative path to a site dir or virtualenv.
    index: sys.path position to insert the site dir.

  Raises:
    ValueError: path doesn't exist.
  """
  venv_path = os.path.join(path, 'lib', PYTHON_VERSION, 'site-packages')
  if os.path.isdir(venv_path):
    site_dir = venv_path
  elif os.path.isdir(path):
    site_dir = path
  else:
    raise ValueError('virtualenv: cannot access %s: '
                     'No such virtualenv or site directory' % path)



  sys_path = sys.path[:]
  del sys.path[index:]
  site.addsitedir(site_dir)
  sys.path.extend(sys_path[index:])