ImportError：/usr/local/lib/python2.7/lib-dynload/_io.so：未定义的符号：_PyCodec_LookupTextEncoding

Question

当我使用命令：pip freeze时，它会显示消息错误：

Traceback (most recent call last):
 File "/usr/local/bin/pip", line 7, in <module>
  from pip import main
  File "/usr/local/lib/python2.7/site-packages/pip/__init__.py", line in <module>
  from pip.utils import get_installed_distributions, get_prog
 File "/usr/local/lib/python2.7/site-packages/pip/utils/__init__.py", line 6, in <module>
 import io
 File "/usr/local/lib/python2.7/io.py", line 51, in <module>
 import _io
 ImportError: /usr/local/lib/python2.7/lib-dynload/_io.so: undefined symbol: _PyCodec_LookupTextEncoding

哪个点子：

/usr/local/bin/pip

哪个python：

/usr/local/bin/python

我不知道为什么会出错！所以我希望有人能帮我解决问题！谢谢。