[Python-ideas] Syntax for passing lambdas to functions

[Ryan]

Last option's way more likely. I made that mistake about 2000 times moving over from C++.

Andrew Barnert <abarnert at yahoo.com> wrote:
>On Feb 27, 2014, at 13:24, Chris Angelico <rosuav at gmail.com> wrote:
>
>> On Fri, Feb 28, 2014 at 8:14 AM, Steven D'Aprano
><steve at pearwood.info> wrote:
>>>>    class A: ...
>>>>    a = A()
>>>>    l = [0]
>>>> 
>>>>    for a.x in [1, 2, 3]: ...
>>>>    for l[0] in [1, 2, 3]: ...
>>> 
>>> I wonder whether that is deliberate feature, or an accident of the
>way
>>> the syntax works. It does seem to be pretty useless though -- why
>are
>>> you using an attribute or list as a loop variable?
>> 
>> I would say it's no accident that the for loop can accept any lvalue.
>> That's how we can do this, which I'm sure you'll agree is *extremely*
>> useful:
>> 
>> for x,y in [(1,2), (3,4), (5,6)]: ...
>> 
>> Assigning to the tuple works beautifully there (especially with
>> enumerate or zip). Being able to assign to other complex targets is a
>> bonus that you'll probably never come across (I can imagine someone
>> might have a use for "for self.blah in ...", but can't concoct any
>> right now)
>
>Something I've seen in real code (not _good_ code, but actually
>deployed):
>
>    for self.index in range(len(self.values)):
>        if self.values[self.index] == spam:
>            break
>    else:
>        self.index = None
>
>Apparently someone didn't want to catch the exception from list.index.
>(Or, more likely, they were trying to write C code in Python.)
>_______________________________________________
>Python-ideas mailing list
>Python-ideas at python.org
>https://mail.python.org/mailman/listinfo/python-ideas
>Code of Conduct: http://python.org/psf/codeofconduct/

-- 
Sent from my Android phone with K-9 Mail. Please excuse my brevity.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-ideas/attachments/20140227/ed650e27/attachment-0001.html>