如何在Mac上更改Python的系统路径？

关于蟒蛇我有个问题

打印sys.path的内容时，系统版本显示在Macports版本之前。如何更改路径，使macports版本永久出现在系统版本之前，我不想在每个程序的开头反转路径。如果您感兴趣，这是整个路径：

['', '/Library/Python/2.7/site-packages/pyglet-1.1.4-py2.7.egg', '/Library/Python/2.7/site-packages/greenlet-0.3.1-py2.7-macosx-10.7-intel.egg', '/Library/Python/2.7/site-packages/cocos2d-0.4.0-py2.7.egg', '/Library/Python/2.7/site-packages/simplejson-2.1.6-py2.7-macosx-10.7-intel.egg', '/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python27.zip', '/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7', '/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plat-darwin', '/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plat-mac', '/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plat-mac/lib-scriptpackages', '/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk', '/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-old', '/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-dynload', '/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages', '/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/PyObjC', '/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/setuptools-0.6c11-py2.7.egg-info', '/Library/Python/2.7/site-packages']

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只需执行以下操作：sys.path.appendthe new path here

这不起作用，因为当我重新启动Python时，路径与以前保持不变，除非我遗漏了一些东西…/usr/local/lib/Python/site包根据Python目录更改它，并在该目录中放置路径文件.pth。路径文件只是简单的文件，每行有一个库路径。