举一个很简单的例子，如果你发现一个包或者模块，明明是有的，但是会发生这样的错误：

>>> from algorithm import *
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named algorithm

那么就应该是环境变量出问题了

okay，来看怎么搞

>>>>> import sys
>>> sys.path
['', '/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']

首先，这些显示出了Python自己的环境变量

然后

>>> sys.path.append('/media/File/Code_DownloadCodeAndSelfCode/PyWorkPlace/xView')
>>> sys.path
['', '/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', '/media/File/Code_DownloadCodeAndSelfCode/PyWorkPlace/xView/emotionAnalyse', '/media/File/Code_DownloadCodeAndSelfCode/PyWorkPlace/xView']
>>> import algorithm

这样，就把自己的algorithm这个包导入了

ok了！

可是这样有个问题，下次还得设置才行。

那么就改一下系统变量吧:

$export PYTHONPATH=$PYTHONPATH:/home/YOURSELFPATH

亲测有效～