当Python执行import语句时，它会在一些路径中搜索Python模块和扩展模块。可以通过sys.path查看这些路径，比如：
>>> import sys
>>> sys.path
['', '/usr/lib/python2.7/site-packages/demo_nova_hooks-5-py2.7.egg', '/usr/lib64/python27.zip', '/usr/lib64/python2.7', '/usr/lib64/python2.7/plat-linux2', '/usr/lib64/python2.7/lib-tk', '/usr/lib64/pytho
