import types import inspect # Modifies class methods (or instances of them) on the fly # http://blog.ianbicking.org/2007/08/08/opening-python-classes/ # http://svn.colorstudy.com/home/ianb/recipes/magicset.py def magic_set(obj): """ Adds a function/method to an object. Uses the name of the first argument as a hint about whether it is a method (``self``), class method (``cls`` or ``klass``), or static method (anything else). Works on both instances and classes. >>> class color: ... def __init__(self, r, g, b): ... self.r, self.g, self.b = r, g, b >>> c = color(0, 1, 0) >>> c # doctest: +ELLIPSIS <__main__.color instance at ...> >>> @magic_set(color) ... def __repr__(self): ... return '' % (self.r, self.g, self.b) >>> c >>> @magic_set(color) ... def red(cls): ... return cls(1, 0, 0) >>> color.red() >>> c.red() >>> @magic_set(color) ... def name(): ... return 'color' >>> color.name() 'color' >>> @magic_set(c) ... def name(self): ... return 'red' >>> c.name() 'red' >>> @magic_set(c) ... def name(cls): ... return cls.__name__ >>> c.name() 'color' >>> @magic_set(c) ... def pr(obj): ... print obj >>> c.pr(1) 1 """ def decorator(func): is_class = (isinstance(obj, type) or isinstance(obj, types.ClassType)) args, varargs, varkw, defaults = inspect.getargspec(func) if not args or args[0] not in ('self', 'cls', 'klass'): # Static function/method if is_class: replacement = staticmethod(func) else: replacement = func elif args[0] == 'self': if is_class: replacement = func else: def replacement(*args, **kw): return func(obj, *args, **kw) try: replacement.func_name = func.func_name except: pass else: if is_class: replacement = classmethod(func) else: def replacement(*args, **kw): return func(obj.__class__, *args, **kw) try: replacement.func_name = func.func_name except: pass setattr(obj, func.func_name, replacement) return replacement return decorator if __name__ == '__main__': import doctest doctest.testmod()