Function name printing should use __qualname__ instead of __name__ (Python 3)

[admk]

There is a bug in the formatting of functions belonging to a class in IPython 2.0.0 running in Python3.

In [1]: class A:
   ...:     def f(self):
   ...:         pass
   ...:

In [2]: A.f
Out[2]: <function __main__.f>

In [3]: str(A.f)
Out[3]: '<function A.f at 0x10b283840>'

The function name formatting is using the __name__ attribute of the function instead of __qualname__, which results in incorrectly showing the function f here in our example belongs to __main__ instead of __main__.A.

A quick fix would be a one line change in https://github.com/ipython/ipython/blob/master/IPython/lib/pretty.py#L749 to use __qualname__ instead, but will break in Python 2.x as there is no __qualname__ support.

def _function_pprint(obj, p, cycle):
    """Base pprint for all functions and builtin functions."""
    if obj.__module__ in ('__builtin__', 'builtins', 'exceptions') or not obj.__module__:
        name = obj.__name__
    else:
        name = obj.__module__ + '.' + obj.__name__  # use obj.__qualname__
    p.text('<function %s>' % name)

[takluyver]

Fixed in #5568.