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?
Regards,
Thomas Bach.
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