syntax questions

[Philippe Gendreau]

* Michael Chermside <mcherm at destiny.com> [2002-07-24 14:16]:
> > I know about the dir() function,  but I'm surprised that my list object
> > hides a function object (even if they have the same name). 
> > Is that how python treats names all the time? Does it mean you can't
> > have a class, def and variable of the same name?
> 
> Yes, that's how it works all the time.
> 
> Actually, the ADVANTAGE of this is that you aren't required to memorize 
> the entire list of all built-in functions and things. For instance, if 
> you NEVER, EVER use the "input" function (as well you shouldn't), then 
> it's not going to hurt you if you use a line like:
> 
>      for input in sys.stdin:
>          process(input)
> 
> Of course, it's still not a good idea, but you aren't forced to memorize 
> the list of built-in stuff, nor does old code break when a new built-in 
> function is added (which happens rarely, but does happen).
> 
> As for having a class, a "def" (ie, function), and a variable all with 
> the same name, no... not in the same namespace. And this is good. 
> Because in Python (unlike some languages), a function, a class, and a 
> "variable", are all objects, and can be used interchangably.
> 
> Consider the map() function. It is normally passed a function as its 
> first argument and applies it to the items in a list:
> 
>      >>> def add5(x):
> 	    return x + 5
>      >>> map( add5, range(4) )
>      [5, 6, 7, 8]
> 
> But classes are instantiated by calling them, as if they were functions. 
> So we can pass a class in, where it expects a function, and it all works 
> just fine:
> 
>      >>> from UserString import UserString
>      >>> map( UserString, range(4) )
>      ['0', '1', '2', '3']
> 
> We could even use a variable to store the item to pass... resulting in 
> code like this:
> 
>      >>> f1 = add5
>      >>> f2 = UserString
>      >>> [ map(f, range(4)) for f in f1, f2]
>      [[5, 6, 7, 8], ['0', '1', '2', '3']]
> 
> So the fact that all things are just "objects" and don't have separate 
> namespaces is highly useful, since it comes closer to making 
> "everything" first class objects, giving the language more power.

Thanks it makes sense, I see where it can be useful.
I think I'm gonna like python...
--
Philippe Gendreau