PEP 308: I liked the original proposal better

Anders Hammarquist iko at cd.chalmers.se
Mon Feb 24 18:20:41 CET 2003


In article <mailman.1046100510.25922.python-list at python.org>,
Dave Brueck  <dave at pythonapocrypha.com> wrote:
>> Short-circuiting and everything else required in one.
>>
>> this-was-going-to-be-a-wink-but-I-like-this-idea-ly yours
>
>Better put the wink back in. :) Unfortunately, it doesn't provide short
>circuiting for any of the times when short-circuiting is actually
>important - it's unlikely that a parameterless function call would be that
>useful, not to mention the more common uses like preventing invalid
>attribute access, preventing divide by zero, etc. :(

Sure it does:
>>> def ifelse(cond, true, false, call=False):
...     if cond:
...         if call:
...             return true()
...         else:
...             return true
...     else:
...         if call:
...             return false()
...         else:
...             return false
... 
>>> a 
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
NameError: name 'a' is not defined
>>> b = 42
>>> ifelse('a' in globals(), lambda : a, lambda : b, True)
42
>>> 

to add additional magic, let call default to None and say:

if call or call is None and callable(true):

and

if call or call is None and callable(false):

and you only need to set call to False if you want to return
a (non-lazy) callable.

/Anders
-- 
 -- Of course I'm crazy, but that doesn't mean I'm wrong.
Anders Hammarquist                                  | iko at cd.chalmers.se
Physics student, Chalmers University of Technology, | Hem: +46 31 88 48 50
G|teborg, Sweden.           RADIO: SM6XMM and N2JGL | Mob: +46 707 27 86 87




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