On 15/08/2012 22:17, Thomas Bach wrote:
Hi list,I'm confronted with a strang problem I cannot find a clean solution for. To me it seems like I need meta-classes. Anyway, I stucked a bit deeper in that topic and couldn't find a proper solution neither. But, judge for yourselve. I want a class that determines on instantiating its base classes dynamically. Consider the following two use cases a = Foo(['a', 'list']) # returns an instance that behaves like a list assert len(a) == 2 assert a[0] == 'a' assert a == ['a', 'list'] assert isinstance(a, list) # This would be nice, but no must-have b = Foo({'blah': 8}) # returns an instance that behaves like a dict assert b['blah'] == 'blah' assert b == {'blah': 8} assert isinstance(b, dict) # again, no must-have a.do_something() # common function to both instances as defined b.do_something() # in the Foo class What I'm currently doing something like the following: class Foo(object): def __init__(self, obj): self._obj = obj def __len__(self): return len(self._obj) def __getitem__(self, name): return self._obj[name] # … def do_something(self): # do something on self._obj pass Which seems ugly. Is there a way to provide the functions of `list' and `dict' in Foo's look-up path without having to write all the stubs myself?
Does Foo have to be a class? Couldn't it just be a factory function? -- http://mail.python.org/mailman/listinfo/python-list
