Home Original page

up with PyGUI!

Bengt Richter bokr at oz.net
Sun Sep 26 17:39:10 EDT 2004 
On 26 Sep 2004 05:35:03 GMT, "OKB (not okblacke)" <brenNOSPAMbarn at NObrenSPAMbarn.net> wrote:

>Bengt Richter wrote:
>
>> myFrame = (
>>   Frame(
>>     Sizer(
>>       CustButton(size= ... etc),
>>       CustButton(size= ... etc),
>>       Panel(
>>         Sizer(
>>           CustListBox(etc),
>>           CustListBox(etc),
>>           CustButton(etc),
>>           Text( etc )
>>         )
>>       )
>>     )
>>   )
>> )
>
>    	One problem with this is that it's not possible to define methods 
>on your widgets in this kind of structure.
                 ^^-- I take it you mean within...
Hm, yes. Need a full lambda or "anonymous def" to do that inline. At least
for non-trivial methods. Wasn't thinking about that. Hm, "not possible" pushes
a button somewhere deep in my psyche though. I guess it's the occasional reward of
discovery that keeps the circuit alive ;-) Not sure ... ;-)

>
>>>If Python's syntax were more flexible, this could perhaps be done
>>>in other ways -- I'm not saying I want that -- but as it is the
>>>only real way to construct nested structures in Python is with
>>>class definitions. 
>> You don't mean that ("...only real way...") as broadly as it
>> sounds, do you? 
>
>    	Sorry, you're right.  Obviously dictionaries and lists can be 
>nested.  A key point, though, is the one I mentioned above: classes are 
>the only structure which allow you define nested structures with 
>arbitrary in-line code.  The "in-line" proviso there may seem obtuse, 
>but I think it's important.  For instance, if you define a button, you 
>should be able to define the event handler for a click on that button 
>right there, as part of writing the button code.  Having to separate the 
>event-handling code out into a separate routine leads to 
>spaghettification, and also introduces a bunch of naming problems (you 
>need to have a consistent naming convention that links a widget to its 
>event handler).
whatever = factory("""
    any source format you like # ;-)
""")
Not entirely kidding.

>
>    	(Also, just for the record: I know you can nest function 
>definitions in other functions, but this isn't useful here because 
I was going to chase down that rabbit trail a bit ;-)
>there's no way to access the nested function definition from outside the 
There you go again, pushing the "no way" button ;-)
>enclosing function, whereas you can reference nested classes with normal 
>attribute access.)

The trouble with accessing nested functions is there's no unboxed way to mutate
closure variables, otherwise I think you could get around the "no way" building
on something like

 >>> def nester(*args, **kw):
 ...     def foo(*a,**k): print 'foo here with', args, a, k
 ...     def bar(*a,**k): print 'bar here with', args, a, k
 ...     def accessnest(self, name, *args, **kw):
 ...         return getattr(self, name)(*args, **kw)
 ...     accessnest.foo = foo
 ...     accessnest.bar = bar
 ...     accessnest.__dict__.update(kw)
 ...     return accessnest.__get__(accessnest)
 ...
 >>> callnested = nester('nester arg', outsider=lambda x: 2*x)
 >>> callnested('foo', 1,2, hi='ho')
 foo here with ('nester arg',) (1, 2) {'hi': 'ho'}
 >>> callnested('bar')
 bar here with ('nester arg',) () {}
 >>> callnested('outsider', ' xxx')
 ' xxx xxx'
 >>> callnested('outsider', 123)
 246

Not that this is crisp and clean and lean as a way of expressing design intent ;-)

Regards,
Bengt Richter
More information about the Python-list mailing list