ImportError: Bad magic number, since OSX Lion

I'm getting this error every time I run any python file in Eclipse using PyDev:

Traceback (most recent call last):
  File "/System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python/sit开发者_开发问答e.py", line 73, in <module>
__boot()
  File "/System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python/site.py", line 2, in __boot
    import sys, imp, os, os.path   
ImportError: Bad magic number in /System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/os.pyc

I'm using python 2.6. This problem does not occur when I run python from the terminal (2.7 or 2.6). The only substantial thing I've changed since everything last worked, is an update to OSX Lion from Snow Leopard.

Similar discussions to this seem to suggest some kind of removal of the .pyc file, because of some kind of mismatch between what was originally using the .pyc files (I'm not entirely sure what a magic number is...). But I was a bit cautious of the idea of deleting os.pyc from the Frameworks directory. When the only other file is an os.pyo file (not sure what the difference it), rather than an os.py.

I've installed all OSX Lion updates, Eclipse updates and PyDev updates.

This problem occurs even with code such as :

if __name__ == '__main__':
    pass

Any help resolving this would be appreciated!

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Upgrading Python to 2.7.1, running "Update Shell Profile" command file which is located in Python directory and changing the Python settings in Netbeans according to new installation worked for me.

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Yeah, you'll need to regenerate all your *.pyc and *.pyo files from the *.py files.

How you do this depends on how they were generated in the first place. Some packaging of python (and it's add-ons), such as in some Linux distros, gets a little too clever for its own good and keeps the original *.py files somewhere else and have their own build system for generating and placing the *.pyc and/or *.pyo files. In a case like that, you have to use that build system to regenerate them from the original *.py files.

FYI, here are a couple links on *.pyo files. They are the optimized versions of compiled python modules.

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On OS X Lion, you should have a os.py file. This is likely the root cause of your error. The os.pyc file was generated from a different version of python than you are running now. Normally, I imagine the python interpreter would just regenerate the file from os.py. But for whatever reason, your system does not have that file.

I suspect that this is a small data point in a larger set of issues and would, in general, recommend a reinstallation of your operating system.

For comparison, I'm running 10.7.1, and I have the following:

[2:23pm][wlynch@orange workout] ls /System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/os.*
/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/os.py
/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/os.pyc
/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/os.pyo

As an aside, the *.pyo file is an optimized version of the python bytecode.