Why aren't colons optional?

[Huaiyu Zhu]

On Sun, 20 Jan 2002 16:39:52 -0500, Roy Smith <roy at panix.com> wrote:
>Alex Martelli <aleax at aleax.it> wrote:
>
>> No, it would have substantially impoverished the language:
>> 
>> class doubleface:
>>     def __getitem__(self, name):
>>         return "anitem"
>>     def __call__(self, *args):
>>         return "acall"
>
>Can you give me a practical example of why somebody would want to define a 
>__getitem__ method for a class?

The UserDict class has __getitem__, as it simulates a dictionary.  I guess
you wanted to ask about __call__.  Here's one example:

from UserDict import UserDict
class Dispatcher(UserDict):
    def __call__(self, cmd_name, *args):
        actual_cmd = self[cmd_name]
        return actual_cmd(*args)

import operator
d = Dispatcher(operator.__dict__)
print d("add", 2, 3)

Huaiyu