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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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if typ is _SENTINEL: |
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f = sys._getframe(framedepth) |
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try: |
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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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typ = find_owner(type_or_obj, f.f_code) |
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except (AttributeError, RuntimeError, TypeError): |
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try: |
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typ = find_owner(type_or_obj.__class__, f.f_code) |
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except AttributeError: |
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raise RuntimeError('super() used with an old-style class') |
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except TypeError: |
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raise RuntimeError('super() called outside a method') |
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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 find_owner(cls, code): |
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'''Find the class that owns the currently-executing method. |
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''' |
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for typ in cls.__mro__: |
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for meth in typ.__dict__.values(): |
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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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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__(cls, typ) |
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except (AttributeError, TypeError): |
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continue |
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if meth.func_code is code: |
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return typ |
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raise TypeError |
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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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