[Python-ideas] Generator syntax hooks?

[Terry Reedy]

On 8/10/2017 9:42 AM, Steven D'Aprano wrote:
> On Wed, Aug 09, 2017 at 01:23:28PM -0700, Chris Barker wrote:
> 
>> I can't recall the use case(s) at the moment, but I have definitely wanted
>> a way to break out of a comprehension -- and not always with infinite
>> iterators.
>>
>> After all, we have "break" in both for and while loops, so clearly there is
>> the use case...

In both cases, we use 'break' to mean break.  If we want to break 
comprehensions, I think we should continue to use 'break' to mean break 
instead of twisting 'while' to mean 'break'.

> [expression for x in sequence while condition]
> 
> should (I believe) be obvious to anyone who already groks comprehension
> syntax. The mapping to a for-loop is admittedly a tad more complex:
> 
> result = []
> for x in sequence:
>      if not condition: break
>      result.append(expression)

This is the same as

result = []
for x in sequence:
     if condition:
         result.append(expression)
     else:
         break

which could be written

[expression for x in sequence if condition break]

-- 
Terry Jan Reedy