Python becoming less Lisp-like

[Steven Bethard]

Kent Johnson wrote:
> Steven Bethard wrote:
> 
>> Bruno Desthuilliers wrote:
>>
>>>> class CommandMenuSelectionCallback:
>>>>     def __init__(self, key):
>>>>         self.key = key
>>>>
>>>>     def __call__(self):
>>>>         print self.key
>>>
>>>
>>> Looks like Java.
>>
>> When was the last time you used Java?  It has no support for using 
>> classes as callable objects.  __call__ would have to be invoked 
>> manually; you definitely couldn't have a CommandMenuSelectionCallback 
>> instance masquerading as a function as this code (basically) does.
> 
> It's like Java in that it uses a short helper class to define an event 
> callback. In the case of Java it would be an anonymous inner class 
> programming to an interface. It's like Java in that it uses five lines 
> of code to do what Python can do in one.

Well the second is definitely true. ;)

> Do you really prefer this verbosity to a lambda expression?

Depends on the situtation.  I do like that the signature of 
CommandMenuSelectionCallback is correct (that is, no arguments), where
     lambda cmd=cmdkey: CommandMenuSelection(cmd)
has an optional argument when one is not asked for.

OTOH, in this particular case, the real problem is that the API has made 
a poor choice for callbacks.  The signature of 
UI.CmdBtn.menu.add_command should be
     add_command(label, command, *args, **kwargs)
instead of
     add_command(label, command)
Of course API's won't always do things the way you want them to, so I 
can see that in working around API deficiences, lambda can occasionally 
seem useful.

STeVe