itertools to iter transition (WAS: Pre-PEP: Dictionary accumulator methods)

[Bengt Richter]

On Tue, 29 Mar 2005 11:32:33 -0800, Michael Spencer <mahs at telcopartners.com> wrote:
[...]
>While we're on the topic, what do you think of having unary, non-summary 
>builtins automatically map themselves when called with an iterable that would 
>otherwise be an illegal argument:
That last "otherwise" is pretty important for strings as in int('1234') ;-)
>
>e.g.,
>int(iterable) -> (int(i) for i in iterable)
>ord(iterable) -> (ord(i) for i in iterable)
>
>
>This would be unambiguous, I think, in the cases of bool, int, callable, chr, 
>float, hex, id, long, oct, ord, vars...

>
>It would shorten the common cases of:
>for char in somestring:
>     ordchar =  ord(char)
>     # do something with ordchar, but not char

But wouldn't you really currently write the "->" form from above? I.e.,

 for ordchar in (ord(c) for c in somestring):
      ...
   
to compare with
>to
>for ordchar in ord(somestring):
>     ...
>
So it's not _that_ much shorter ;-)

>It would not work for summarizing functions or those that can accept an iterable 
>today e.g., len, repr
>
I like concise expression, so I'm willing to try it. I guess it would be enough
to override __builtins__ to get a taste, e.g., (not thought through):

 >>> class itint(int):
 ...     oldint = __builtins__.int
 ...     def __new__(cls, arg):
 ...         try: return cls.oldint(arg)
 ...         except (TypeError, ValueError):
 ...             oi = cls.oldint
 ...             return (oi(item) for item in arg)
 ...
 >>> __builtins__.int = itint
 >>> int('1234')
 1234
 >>> for x in int('1 23 456'.split()): print x,
 ...
 1 23 456
 >>> for x in int(range(1,8,2)): print x,
 ...
 1 3 5 7
 >>> for x in int('123x'): print x,
 ...
 1 2 3
 Traceback (most recent call last):
   File "<stdin>", line 1, in ?
   File "<stdin>", line 7, in <generator expression>
 ValueError: invalid literal for int(): x

Hm, ... ;-)

Regards,
Bengt Richter