how to assert that method accepts specific types

[Scott David Daniels]

Rhodri James wrote:
> On Sat, 21 Feb 2009 01:12:01 -0000, Darren Dale <dsdale24 at gmail.com> wrote:
>> I would like to assert that a method accepts certain types....
>>     from functools import wraps
>>     def accepts(*types):
>>         def check_accepts(f): ...
>>     class Test(object):
>>         @accepts(int)
>>         def check(self, obj):
>>             print obj
>> but now I want Test.check to accept an instance of Test as well....
> 
> An icky but relatively clear way to get around this is to gratuitously
> subclass Test:
> class AcceptableTest(object):
>     pass
> 
> class Test(AcceptableTest):
>     @accepts(int, AcceptableTest)
>     def check(self, obj):
>         print obj

To Increase the ick, but lowering the name pollution
(while making the _source_ read more clearly):

     class Test(<Test base classes>):
         pass # Just a placeholder for type checking

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


--Scott David Daniels
Scott.Daniels at Acm.Org