10.08.17 17:28, Steve D'Aprano пише:
Every few years, the following syntax comes up for discussion, with some people
saying it isn't obvious what it would do, and others disagreeing and saying
that it is obvious. So I thought I'd do an informal survey.
What would you expect this syntax to return?
[x + 1 for x in (0, 1, 2, 999, 3, 4) while x < 5]
I would expect it to be equivalent to the following code:
result = []
for x in (0, 1, 2, 999, 3, 4):
while x < 5:
result.append(x + 1)
This is an infinite loop.
For comparison, what would you expect this to return? (Without actually trying
it, thank you.)
[x + 1 for x in (0, 1, 2, 999, 3, 4) if x < 5]
result = []
for x in (0, 1, 2, 999, 3, 4):
if x < 5:
result.append(x + 1)
How about these?
[x + y for x in (0, 1, 2, 999, 3, 4) while x < 5 for y in (100, 200)]
result = []
for x in (0, 1, 2, 999, 3, 4):
while x < 5:
for y in (100, 200):
result.append(x + y)
[x + y for x in (0, 1, 2, 999, 3, 4) if x < 5 for y in (100, 200)]
result = []
for x in (0, 1, 2, 999, 3, 4):
if x < 5:
for y in (100, 200):
result.append(x + y)
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