[Python-ideas] Is this PEP-able? for X in ListY while conditionZ:

[Joshua Landau]

On 1 July 2013 16:21, Shane Green <shane at umbrellacode.com> wrote:
>
> Having a bit of a hard time following the status of this as I dropped out
for a while, but I’m not really for the semi-colon separator approach.  Of
all the options already available in list comprehensions, this one actually
seems to be one of the most easily because it starts with a keyword and
ends at the end.  Not that syntax highlighting should be taken into account
in general, it’s worth noting the syntax highlighted version really makes
this distinction quite clear:
<IMG>

That's somewhat convincing. I'm still not convinced we need new syntax
though. \

> One thing I could see doing would be to allow semi-colons anywhere in a
 list comprehension that’s a boundary between statements of the expanded
form.
>
> Then they behave just like the optional semi-colons you could put at the
end of a line.
>
> Sorry if that’s precisely what’s been promoted. .

So (I'm just adding examples to your idea):

    [item for sublist in data for item in sublist; if item]

can become

    [item; for sublist in data; for item in sublist; if item]


In a pathological case this is a transform from:

    [item for sublist in data if sublist for item in sublist if item%3 if
item-1]

to

    [item for sublist in data; if sublist; for item in sublist; if item%3;
if item-1]

But you can always do:

    [item
     for sublist in data if sublist
     for item in sublist if item%3
                         if item-1]


That said, it's not like people *do* those sorts of pathological
expressions, is it?
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