how to assert that method accepts specific types

Darren Dale dsdale24 at
Fri Feb 20 20:12:01 EST 2009

I would like to assert that a method accepts certain types. I have a
short example that works:

from functools import wraps

def accepts(*types):
    def check_accepts(f):
        def new_f(self, other):
            assert isinstance(other, types), \
                "arg %r does not match %s" % (other, types)
            return f(self, other)
        return new_f
    return check_accepts

class Test(object):

    def check(self, obj):
        print obj

t = Test()

but now I want Test.check to accept an instance of Test as well. Does
anyone know how this can be accomplished? The following class
definition for Test raises a NameError:

class Test(object):

    @accepts(int, Test)
    def check(self, obj):
        print obj


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