[Swig-devel] [ swig-Bugs-2583160 ] import code breaks loading of several modules in one binary

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Bugs item #2583160, was opened at 2009-02-09 17:50
Message generated for change (Comment added) made by sirkne
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Category: python
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Gaetan Lehmann (gleh)
Assigned to: Nobody/Anonymous (nobody)
Summary: import code breaks loading of several modules in one binary

Initial Comment:
Previously, it was possible to link several modules in a single binary. The modules where loaded from the main init_Module() function. This is a very useful feature for huge libraries and build systems limited to a few binary produced (msvc for exampe).

Now we can't do that in python 2.6, because of the code used to import the module in the shadow classes, which explicitly search for the module file with imp.find_module() which obviously doesn't exist in that case.

if version_info >= (2,6,0):
    def swig_import_helper():
        from os.path import dirname
        import imp
        try:
            fp, pathname, description = imp.find_module('_itkImagePython', [dirname(__file__)])
            _mod = imp.load_module('_itkImagePython', fp, pathname, description)
        finally:
            if fp is not None: fp.close()
        return _mod
    _itkImagePython = swig_import_helper()
    del swig_import_helper
else:
    import _itkImagePython

If I understand correctly, this code has been introduced to fix the syntax error with older python and explicit relative import. The exec statement doesn't seem to be usable, so here is how it can be implemented to preserve the ability to link several modules in one:

if version_info >= (2,6,0):
    def swig_import_helper():
        from os.path import dirname
        import imp
        fp = None
        try:
            # search for the module
            fp, pathname, description = imp.find_module('_itkImagePython', [dirname(__file__)])
        except ImportError:
            # not found - try to simply import it, in case it is already loaded
            import _itkImagePython
            return _itkImagePython
        if fp is not None:
            # module has been found - lets load it
            try:
                _mod = imp.load_module('_itkImagePython', fp, pathname, description)
            finally:
                fp.close()
            return _mod
    _itkImagePython = swig_import_helper()
    del swig_import_helper
else:
    import _itkImagePython



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Comment By: Ken Lauer (sirkne)
Date: 2009-02-23 14:09

Message:
The current code also breaks py2exe support for SWIG on Python 2.6:

File "mylibrary\mylibrary.pyc", line 20, in swig_import_helper:
  UnboundLocalError: local variable 'fp' referenced before assignment

As it fails with an ImportError. The standard "import _mylibrary" works.

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You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=101645&aid=2583160&group_id=1645