[Python-ideas] Reuse "for" to express "given"
alexander.belopolsky at gmail.com
Thu May 24 11:54:09 EDT 2018
I have read most of the PEP 572 related threads, but I don't think I've
seen this idea. As many other people mentioned, Python already allows a
trick to introduce local bindings in generator expressions and list
comprehensions. This can be achieved by adding a "for var in [<expr>]"
clause. I propose to make "for var = <expr>" have the same effect as "for
var in [<expr>]".
Note that in the case of filters, the order will be different from that in
the original "given" proposal: instead of
[(x, y, x/y) for x in data if y given y = f(x)]
we will write
[(x, y, x/y) for x in data for y = f(x) if y]
The use of "for" in place of "given" in the if statements does not look too
if m for m = pattern.search(data):
elif m for m = other_pattern.search(data)):
I have to admit that
while m for m = pattern.search(remaining_data):
looks strange at first because both while and for are strongly associated
with loops, but if you read "for var = <expr>" as "for var equals
expression", the difference between that and "for var in (iterable)
expression" becomes apparent.
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