gobject-introspection overrides cause import errors

Question

I am using gobject-introspection in python2.7 on ubuntu raring and I run into an import error while building some packages. I have isolated a minimal set of steps to replicate it:

1. Make a local directory structure:

   gi:
           __init__.py
           overrides:
                   __init__.py
   

2. Put the standard boilerplate

   from pkgutil import extend_path
   
   __path__ = extend_path(__path__, __name__)
   print __path__, __name__
   

   in both __init__.py files.

3. From the directory containing your local copy of gi, run the following:

   python -c "from gi import repository"
   

4. I get an error message that looks like:

   Traceback (most recent call last):
     File "<string>", line 1, in <module>
     File "/usr/lib/python2.7/dist-packages/gi/repository/__init__.py", line 25, in         <module>
       from ..importer import DynamicImporter
     File "/usr/lib/python2.7/dist-packages/gi/importer.py", line 28, in <module>
       from .module import DynamicModule
     File "/usr/lib/python2.7/dist-packages/gi/module.py", line 37, in <module>
       from .overrides import registry
   ImportError: cannot import name registry
   

Any explanation? I can't find any decent documentation of the intended behavior because gobject-introspection seems like a very poorly documented project. Help is greatly appreciated!

Answer 1

From the Python documentation:

The __init__.py files are required to make Python treat the directories as containing packages; this is done to prevent directories with a common name, such as string, from unintentionally hiding valid modules that occur later on the module search path.

Simply by having those __init__.py files accessible from the running directory, you are telling the interpreter that that is an implementation of the gi module. Any usage of the main gi module will not go correctly.

Now, why does it print the error as coming from /usr/lib ? Because gi was found in local/gi, but gi.repository was found in /usr/lib/python2.7/dist-packages/gi/repository . It is running /usr/lib/python2.7/dist-packages/gi/repository/__init__.py. From there, it imports some other submodules correctly, but when it tries to import overrides it finds your local stub in gi/overrides. Your stub does not define registry, so you have the fail.

Try and put registry='dumb_string' in gi/overrides/__init__.py and see that the error is gone.