"no matching architecture in universal wrapper" problem in wxPython?

Question

I am running Python 2.7 under Mac OS 10.6.4, and I just installed wxPython from the wxPython2.8-osx-unicode-2.8.11.0-universal-py2.7.dmg binary. I am getting a weird error on the import wx line in my Python scripts. FYI, I can import the wx module just fine from PyCrust. I don't really see what I have done wrong here. Could anyone please assist?

  File "prod_cons_wx.py", line 6, in <module>
    import wx 
  File "/usr/local/lib/wxPython-unicode-2.8.11.0/lib/python2.7/site-packages/wx-2.8-mac-unicode/wx/__init__.py", line 45, in <module>
    from wx._core import *
  File "/usr/local/lib/wxPython-unicode-2.8.11.0/lib/python2.7/site-packages/wx-2.8-mac-unicode/wx/_core.py", line 4, in <module>
    import _core_
ImportError: dlopen(/usr/local/lib/wxPython-unicode-2.8.11.0/lib/python2.7/site-packages/wx-2.8-mac-unicode/wx/_core_.so, 2): no suitable image found.  Did find:
    /usr/local/lib/wxPython-unicode-2.8.11.0/lib/python2.7/site-packages/wx-2.8-mac-unicode/wx/_core_.so: no matching architecture in universal wrapper

Answer 1

It appears that C extension modules included with the wxPython 2.7 dmg here are 32-bit only.

$ cd /usr/local/lib/wxPython-unicode-2.8.11.0/lib/python2.7/site-packages/wx-2.8-mac-unicode/wx
$ file *.so
_animate.so:   Mach-O universal binary with 2 architectures
_animate.so (for architecture ppc): Mach-O bundle ppc
_animate.so (for architecture i386):    Mach-O bundle i386
_aui.so:       Mach-O universal binary with 2 architectures
_aui.so (for architecture ppc): Mach-O bundle ppc
_aui.so (for architecture i386):    Mach-O bundle i386
...

Unfortunately, platform.architecture() does not give an accurate indication of which arch an OS X multiple architecture Python is running in. For example, using the 3-arch python.org installer for Python 2.7, platform.architecture() always reports 64-bit even when running in 32-bit mode:

$ cd /Library/Frameworks/Python.framework/Versions/2.7
$ file python2.7
python2.7: Mach-O universal binary with 3 architectures
python2.7 (for architecture i386):  Mach-O executable i386
python2.7 (for architecture ppc7400):   Mach-O executable ppc
python2.7 (for architecture x86_64):    Mach-O 64-bit executable x86_64
$ arch -x86_64 ./python2.7 -c 'import platform, sys; print "{0}, {1:x}".format(platform.architecture()[0], sys.maxint)'
64bit, 7fffffffffffffff
$ arch -i386 ./python2.7 -c 'import platform, sys; print "{0}, {1:x}".format(platform.architecture()[0], sys.maxint)'
64bit, 7fffffff
$ arch -ppc ./python2.7 -c 'import platform, sys; print "{0}, {1:x}".format(platform.architecture()[0], sys.maxint)'
64bit, 7fffffff

The reliable way is to examine sys.maxint for Python 2 or sys.maxsize for Python 3.

You don't indicate in your question how you invoke Python. Is it via a shebang line in a script file? If so, you may not be running the Python you think you are. Also, you don't indicate which Python 2.7 you have installed. For instance, there are currently two installers for Python 2.7 from python.org: one supports both 32- and 64-bit execution, the other is 32-bit only. Try the following:

$ file $(python2.7 -c 'import sys;print(sys.executable)')
/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python: Mach-O universal binary with 3 architectures
/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python (for architecture i386):   Mach-O executable i386
/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python (for architecture ppc7400):    Mach-O executable ppc
/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python (for architecture x86_64): Mach-O 64-bit executable x86_64

So: if you have a multi-arch version of Python, you'll need to force it to run in 32-bit mode to make use of the pre-compiled wxPython.