115 lines
4.0 KiB
Python
115 lines
4.0 KiB
Python
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'''
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This module provides a newsuper() function in Python 2 that mimics the
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behaviour of super() in Python 3. It is designed to be used as follows:
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from __future__ import division, absolute_import, print_function
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from future.builtins import super
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And then, for example:
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class VerboseList(list):
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def append(self, item):
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print('Adding an item')
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super().append(item) # new simpler super() function
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Importing this module on Python 3 has no effect.
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This is based on (i.e. almost identical to) Ryan Kelly's magicsuper
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module here:
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https://github.com/rfk/magicsuper.git
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Excerpts from Ryan's docstring:
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"Of course, you can still explicitly pass in the arguments if you want
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to do something strange. Sometimes you really do want that, e.g. to
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skip over some classes in the method resolution order.
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"How does it work? By inspecting the calling frame to determine the
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function object being executed and the object on which it's being
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called, and then walking the object's __mro__ chain to find out where
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that function was defined. Yuck, but it seems to work..."
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'''
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from __future__ import absolute_import
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import sys
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from types import FunctionType
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from future.utils import PY3, PY26
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_builtin_super = super
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_SENTINEL = object()
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def newsuper(typ=_SENTINEL, type_or_obj=_SENTINEL, framedepth=1):
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'''Like builtin super(), but capable of magic.
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This acts just like the builtin super() function, but if called
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without any arguments it attempts to infer them at runtime.
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'''
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# Infer the correct call if used without arguments.
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if typ is _SENTINEL:
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# We'll need to do some frame hacking.
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f = sys._getframe(framedepth)
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try:
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# Get the function's first positional argument.
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type_or_obj = f.f_locals[f.f_code.co_varnames[0]]
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except (IndexError, KeyError,):
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raise RuntimeError('super() used in a function with no args')
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try:
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# Get the MRO so we can crawl it.
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mro = type_or_obj.__mro__
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except (AttributeError, RuntimeError): # see issue #160
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try:
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mro = type_or_obj.__class__.__mro__
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except AttributeError:
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raise RuntimeError('super() used with a non-newstyle class')
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# A ``for...else`` block? Yes! It's odd, but useful.
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# If unfamiliar with for...else, see:
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#
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# http://psung.blogspot.com/2007/12/for-else-in-python.html
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for typ in mro:
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# Find the class that owns the currently-executing method.
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for meth in typ.__dict__.values():
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# Drill down through any wrappers to the underlying func.
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# This handles e.g. classmethod() and staticmethod().
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try:
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while not isinstance(meth,FunctionType):
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if isinstance(meth, property):
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# Calling __get__ on the property will invoke
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# user code which might throw exceptions or have
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# side effects
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meth = meth.fget
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else:
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try:
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meth = meth.__func__
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except AttributeError:
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meth = meth.__get__(type_or_obj, typ)
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except (AttributeError, TypeError):
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continue
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if meth.func_code is f.f_code:
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break # Aha! Found you.
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else:
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continue # Not found! Move onto the next class in MRO.
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break # Found! Break out of the search loop.
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else:
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raise RuntimeError('super() called outside a method')
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# Dispatch to builtin super().
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if type_or_obj is not _SENTINEL:
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return _builtin_super(typ, type_or_obj)
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return _builtin_super(typ)
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def superm(*args, **kwds):
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f = sys._getframe(1)
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nm = f.f_code.co_name
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return getattr(newsuper(framedepth=2),nm)(*args, **kwds)
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__all__ = ['newsuper']
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