for / while else doesn't make sense

[Christopher Reimer]

On 5/20/2016 8:59 AM, Zachary Ware wrote:

> On Fri, May 20, 2016 at 3:09 AM, Erik <python at lucidity.plus.com> wrote:
>> On 20/05/16 00:51, Gregory Ewing wrote:
>>> It's not so bad with "else" because you need to look back
>>> to find out what condition the "else" refers to anyway.
>>
>> With my tongue only slightly in my cheek, if it was desirable to
>> "fix"/clarify this syntax then I would suggest adding some optional
>> (existing) trailing keywords to 'else' in this context that spells it out:
>>
>> for item in seq:
>>      if foo(item):
>>          break
>> else if not break:
>>      nomatch()
> With tongue firmly cheeked, you can always use the special `:#` operator:
>
>     for item in seq:
>         if foo(item):
>             break
>     else:# if no break:
>         nomatch()
>
> This has the benefit that you can use whatever syntax you like after
> the `:#`, and use it in any version of Python you want.

According to "Effective Python: 59 Specific Ways to Write Better Python" 
by Brett Slatkin, Item 12 recommends against using the else block after 
for and while loops (see page 25): "Avoid using else blocks after loops 
because their behavior isn't intuitive and can be confusing."

Until I read the book, I wasn't aware of this feature (or bug). Doesn't 
seem like a feature I would use since it's not commonly found in other 
programming languages. As the author demonstrates in his book, I would 
probably write a helper function instead.

Item 13 does recommend using the else block for try/except/else/finally 
in exception handling. :)

Thank you,

Chris R.