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～