Behavior of the for-else construct

[Barry Scott]

> On 3 Mar 2022, at 13:24, computermaster360 <computermaster360 at gmail.com> wrote:
> 
> I want to make a little survey here.
> 
> Do you find the for-else construct useful?

No. I always have to look up what condition the else fires on.

> Have you used it in
> practice?

No.

> Do you even know how it works, or that there is such a thing
> in Python?

Yes (when I read the docs) and yes.

> I have used it maybe once. My issue with this construct is that
> calling the second block `else` doesn't make sense; a much more
> sensible name would be `then`.

There was a thread on this list asking for alternative syntax for the
for: else: that was not taken up. Something like nobreak: instead of else: 

> 
> Now, imagine a parallel universe, where the for-else construct would
> have a different behavior:
> 
>    for elem in iterable:
>        process(elem)
>    else:
>        # executed only when the iterable was initially empty
>        print('Nothing to process')
> 
> Wouldn't this be more natural? I think so. Also, I face this case much
> more often than having detect whether I broke out of a loop early
> (which is what the current for-else construct is for).

> 
> Now someone may argue that it's easy to check whether the iterable is
> empty beforehand. But is it really? What if it's an iterator?
> Then one would have to resort to using a flag variable and set it in
> each iteration of the loop. An ugly alternative would be trying to
> retrieve
> the first element of the iterable separately, in a try block before
> the for-loop, to find out whether the iterable is empty. This would of
> course
> require making an iterator of the iterable first (since we can't be
> sure it is already an iterator), and then -- if there are any elements
> -- processing
> the first element separately before the for-loop, which means
> duplicating the loop body. You can see the whole thing gets really
> ugly really quickly...
> 
> What are your thoughts? Do you agree? Or am I just not Dutch enough...?

Barry

> -- 
> https://mail.python.org/mailman/listinfo/python-list
>