Using contextlib with cython

I am interested in using contextlib with a cdef class in cython in order to nicely wrap some OpenGL code. I had asked this question on stackoverflow. While the workaround I had received worked (using __enter__ and __exit__),

Here is the test code for vbo.pyx that was in that answer for reference:

import contextlib

cdef class Vbo:

    def __init__(self):
        pass

    @contextlib.contextmanager
    def bind(self):
        self.do_something()
        try:
            yield
        finally:
            print("Finally")

    def do_something(self):
        print("something")

This code works for me if I remove the cdef but this should not be necessary. If I use the sample code as is, I get an error message like this when I use that cdef class from python:

Traceback (most recent call last):
  File "main.py", line 2, in <module>
    import vbo
  File "vbo.pyx", line 21, in init vbo (vbo.c:15766)
    @contextlib.contextmanager
  File "C:\Python27\lib\contextlib.py", line 82, in contextmanager
    @wraps(func)
  File "C:\Python27\lib\functools.py", line 33, in update_wrapper
    setattr(wrapper, attr, getattr(wrapped, attr))
AttributeError: 'method_descriptor' object has no attribute '__module__'

It appears that this behavior might be a possible regression as this works apparently in cython 0.25.1 and python 3.6.1. I am using cython 0.25.2 and python 2.7.12.

[rainwoodman]

Hi, I bumped into this issue and realized the documentation of the ‘binding’ directive may need some additional explanation by adding an example (such as this case). Reading it twice I still have little clue what ‘like len’ and ‘binding to an instance’ really means. Thanks! (actually perhaps all of the directives need more documentation…)

[jdemeyer]

Allow me to point to a blogpost of mine which explains some of this: http://opendreamkit.org/2017/06/09/CythonSphinx/