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Emulating classmethod in Python 2.1

Thomas Heller theller at python.net
Thu Jun 6 13:24:23 EDT 2002 
"Hamish Lawson" <hamish_lawson at yahoo.co.uk> wrote in message news:915a998f.0206060833.12ad76a8 at posting.google.com...
> Is it possible to define a 'classmethod' class or function for Python
> 2.1 that would effectively provide the functionality of Python 2.2's
> built-in classmethod function and have the same usage pattern? I'd
> like to be able run code like that below against both 2.2 (using its
> builtin classmethod function) and 2.1 (using some added-in wrapper).
>
>     class SomeClass:
>         def hello(cls, name):
>             print "Hi there", cls, name
>         hello = classmethod(hello)
>
>     SomeClass.hello("Peter")
>
> I've come across Thomas Heller's recipe in the online Python Cookbook,
> but this would require SomeClass to be modified, and so fails my
> criteria.
>
Here's the closest I came up with (you must rewrite your code to
derive SomeClass from object, the rest can remain unchanged).

Thomas

-----------

try:
    object
except NameError:
    class classmethod:
        def __init__(self, func):
            self.func = func

    class _ClassMethod:
        def __init__(self, cls, func):
            self.cls = cls
            self.func = func

        def __call__(self, *args, **kw):
            return self.func(self.cls, *args, **kw)

    import ExtensionClass
    object = ExtensionClass.Base
    class object(ExtensionClass.Base):
        def __class_init__(cls):
            d = {}
            for name, value in cls.__dict__.items():
                if isinstance(value, classmethod):
                    d[name] = _ClassMethod(cls, value.func)
            cls.__dict__.update(d)

#######

class SomeClass(object):

    def hello(cls, name):
        print "Hi there", cls, name
    hello = classmethod(hello)

SomeClass.hello("Peter")
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