There are many issues on tracker related to the relative paths in co_filename. Most of them are about introspection functions in inspect module--which are usually broken after 'os.chdir'. 

Test case: create a file t.py:

   def foo(): pass
   print(foo.__code__.co_filename)

Execute it with '$ python t.py' -> it will print 't.py'.

Ideally, when executing a python file, interpreter should expand all relative paths for __file__ and __code__.co_filename attributes.