IPython 导入失败和 python sys.path 一般情况

我正在关注这个post让一个 ipython 统治所有 virtualenvs。

据我了解，这篇文章的主要思想是，当在 virtualenv 中时，ipython 找不到它的模块。

(a-virtualenv)me@pc:~$ ipython
Traceback (most recent call last):
  File "/usr/bin/ipython", line 19, in <module>
    from IPython.frontend.terminal.ipapp import launch_new_instance
ImportError: No module named IPython.frontend.terminal.ipapp

为了解决这个问题，我将其添加到我的 /usr/bin/ipython

import sys
if "/usr/lib/python2.7/dist-packages" not in sys.path:
    sys.path.append("/usr/lib/python2.7/dist-packages")

这个伎俩对巴尔萨扎很管用。但就我而言，我明白了

Traceback (most recent call last):
  File "/usr/bin/ipython", line 18, in <module>
    from IPython.frontend.terminal.ipapp import launch_new_instance
  File "/usr/lib/python2.7/dist-packages/IPython/__init__.py", line 46, in <module>
    from .frontend.terminal.embed import embed
  File "/usr/lib/python2.7/dist-packages/IPython/frontend/terminal/embed.py", line 37, in <module>
    from IPython.frontend.terminal.ipapp import load_default_config
  File "/usr/lib/python2.7/dist-packages/IPython/frontend/terminal/ipapp.py", line 38, in <module>
    from IPython.core.completer import IPCompleter
  File "/usr/lib/python2.7/dist-packages/IPython/core/completer.py", line 84, in <module>
    from IPython.utils import generics
  File "/usr/lib/python2.7/dist-packages/IPython/utils/generics.py", line 19, in <module>
    from IPython.external.simplegeneric import generic
  File "/usr/lib/python2.7/dist-packages/IPython/external/simplegeneric/__init__.py", line 4, in <module>
    from _simplegeneric import *
ImportError: No module named _simplegeneric

我想也许我应该添加/usr/lib/python2.7/dist-packages/IPython/external to sys.path in /usr/bin/ipython以及。我得到的是

Traceback (most recent call last):
  File "/usr/bin/ipython", line 18, in <module>
    from IPython.frontend.terminal.ipapp import launch_new_instance
  File "/usr/lib/python2.7/dist-packages/IPython/__init__.py", line 43, in <module>
    from .config.loader import Config
  File "/usr/lib/python2.7/dist-packages/IPython/config/loader.py", line 27, in <module>
    from IPython.utils.path import filefind, get_ipython_dir
  File "/usr/lib/python2.7/dist-packages/IPython/utils/path.py", line 24, in <module>
    from IPython.utils.process import system
  File "/usr/lib/python2.7/dist-packages/IPython/utils/process.py", line 27, in <module>
    from ._process_posix import _find_cmd, system, getoutput, arg_split
  File "/usr/lib/python2.7/dist-packages/IPython/utils/_process_posix.py", line 27, in <module>
    from IPython.utils import text
  File "/usr/lib/python2.7/dist-packages/IPython/utils/text.py", line 27, in <module>
    from IPython.external.path import path
ImportError: cannot import name path

这个错误发生在第43行IPython/__init__py，但前一个发生在第 46 行。

1. 如何让 ipython 与 virtualenv 一起工作？

2. 怎么可以添加/usr/lib/python2.7/dist-packages/IPython/external to sys.path导致新的错误？

3. 我应该阅读什么才能更好地理解 python 导入路径？

Thanks!

附： 普通 IPython sys.path

['',
 '/usr/bin',
 '/usr/lib/python2.7',
 '/usr/lib/python2.7/plat-linux2',
 '/usr/lib/python2.7/lib-tk',
 '/usr/lib/python2.7/lib-old',
 '/usr/lib/python2.7/lib-dynload',
 '/usr/local/lib/python2.7/dist-packages',
 '/usr/lib/python2.7/dist-packages',
 '/usr/lib/python2.7/dist-packages/PIL',
 '/usr/lib/python2.7/dist-packages/gst-0.10',
 '/usr/lib/python2.7/dist-packages/gtk-2.0',
 '/usr/lib/pymodules/python2.7',
 '/usr/lib/python2.7/dist-packages/ubuntu-sso-client',
 '/usr/lib/python2.7/dist-packages/ubuntuone-client',
 '/usr/lib/python2.7/dist-packages/ubuntuone-control-panel',
 '/usr/lib/python2.7/dist-packages/ubuntuone-couch',
 '/usr/lib/python2.7/dist-packages/ubuntuone-installer',
 '/usr/lib/python2.7/dist-packages/ubuntuone-storage-protocol',
 '/usr/lib/python2.7/dist-packages/IPython/extensions']

IPython 似乎现在可以工作了！

因为ipython找不到simplegeneric。我试图找到 simplegeneric 并发现 simplegeneric 位于“/usr/lib/pymodules/python2.7”中。添加“/usr/lib/pymodules/python2.7”后，ipython 工作正常。

杰夫·特拉特纳的评论真的很有帮助！