[Pythonmac-SIG] python 2.7 problem with crcmod -- "ImportError: No module named predefined"

Ronald Oussoren ronaldoussoren at mac.com
Tue May 3 12:34:59 CEST 2011

On 3 May, 2011, at 10:37, Brendan Simon (eTRIX) wrote:

> On 3/05/11 5:01 PM, Ronald Oussoren wrote:
>> The crcmod package contains a module named crcmod. My guess is that
>> both py2app and py2exe get confused by this and try to fetch
>> 'crcmod.predefined' from the nested module instead of the toplevel
>> package.  This basicly means that both py2*s have a bug in their
>> emulation of the __import__ code.  
>>>> I'll see if I can create a testcase for this for the modulegraph
>>>> package, it should then be fairly easy to actually fix the issue. As
>>>> this is only a problem with python2.7 this may end up being a bug in
>>>> the stdlib though.
>>>> As a workaround try adding includes for crcmod.predefined, or even
>>>> the entire crcmod package (setup(..., package=['crcmod'], ...))
>>> Yep.  Forcing inclusion of the module in setup does resolve the
>>> issue.  Here is the snippet of my setup file that worked for me :)
>>> Hopefully py2app can be fixed so this is not necessary, but at least
>>> I have a workaround now.
>> I think I can fix this in modulegraph, I'm not quite sure why it works
>> in 2.6 but not in 2.7 though. Are you using the same version of crcmod
>> in both cases?
>> My current impresssion of what's going on here: crcmod.__init__ contains:
>> try:
>>    from crcmod.crcmod import *
>>    import crcmod.predefined
>> except ImportError:
>>    # Make this backward compatible
>>    from crcmod import *
>>    import predefined
>> A test with a simular package structure fails on both 2.6 and 2.7, but
>> works with 3.2. Modulegraph fails because it creates a MissingModule
>> node for crcmod.predefined, which seems to indicate a bug in how we
>> process imports in a package as it should have created a MissingModule
>> node for crcmod.crcmod.predefined for the second import statement and
>> then a real node for the last one.
> Ah, yes, there are different versions of crcmod installed.
> $ /Library/Frameworks/Python.framework/Versions/2.5/bin/pip freeze |
> grep crcmod
> crcmod==1.5
> $ /Library/Frameworks/Python.framework/Versions/2.6/bin/pip freeze |
> grep crcmod
> crcmod==1.6.1
> $ /Library/Frameworks/Python.framework/Versions/2.7/bin/pip freeze |
> grep crcmod
> crcmod==1.7

That explains the difference in behaviour.   I've pushed a fix to the bitbucket repository (at http://bitbucket.org/ronaldoussoren/modulegraph) that should fix this issue.

I'll push out a new release of modulegraph when I've done some more testing.

> -- Brendan.
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