[Python-ideas] Integrate some itertools into the Python syntax

[Sven R. Kunze]

On 23.03.2016 23:18, Michael Selik wrote:
>
>
> On Wed, Mar 23, 2016, 5:55 PM Sven R. Kunze <srkunze at mail.de 
> <mailto:srkunze at mail.de>> wrote:
>
>
>
>     On 23.03.2016 22:44, Michael Selik wrote:
>>
>>
>>     On Wed, Mar 23, 2016, 5:27 PM João Bernardo <jbvsmo at gmail.com
>>     <mailto:jbvsmo at gmail.com>> wrote:
>>
>>         On Mon, Mar 21, 2016 at 8:06 PM, Michel Desmoulin
>>         <desmoulinmichel at gmail.com
>>         <mailto:desmoulinmichel at gmail.com>> wrote:
>>
>>             Itertools is great, and some functions in it are more
>>             used than others:
>>
>>             - islice;
>>             - chain;
>>             - dropwhile, takewhile;
>>
>>
>>         I like how dropwhile and takewhile could be easily integrated
>>         with list comprehensions / generator expressions:
>>
>>         [x for x in range(10) while x < 5]      # takewhile
>>         [x for x in range(10) not while x < 5]  # dropwhile
>>         [x for x in range(10) from x >= 5]      # forward thinking
>>         dropwhile
>>
>>         I believe this is almost plain english without creating new
>>         keywords.
>>
>>
>>     They read well, except for the square brackets which to me imply
>>     consuming the entire iterator. Itertools takewhile will early
>>     exit, possibly leaving some values on the iterator. If these do
>>     consume the entire iterator, what's the difference with the
>>     ``if`` clause in a comprehension?
>
>     But isn't that their purpose? Not consuming. I think that would be
>     easy to learn. +1 on this proposal.
>
>     This could also prove useful to avoid for-else. :-)
>
>
> After the execution of the list comprehension using "while" if the 
> condition triggered halfway, would there be anything left in the 
> original iterator? If it was a generator expression, we'd say "Yes" 
> immediately. As a list comprehension, I'm not sure.

Let's define it this way. Feeling better? ;-)

Best,
Sven
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