PEP 572: Assorted fixes suggested by Rob Cliffe by gvanrossum · Pull Request #719 · python/peps
| ... | ||
| # A loop that can't be trivially rewritten using 2-arg iter() | ||
| while (value := read_next_item(file)) is not None: | ||
| # Do something with value |
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Ick - this example seems wholly contrived. How about keeping the original # A more explicit ... comment but changing the example to match it?
Before:
for line in iter(somefile.readline, ""):
process(line)
After:
while line := somefile.readline():
process(line)
Maybe that just especially appeals to me because I can never remember what 2-arg iter() does ☹️
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The problem with file based examples is that they typically collapse down to for line in somefile: ... in real code. It really is only in cases where native iteration support isn't available for some reason that you need to resort to the loop-and-a-half pattern instead.
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Another real-world example involving files is:
while chunk := somefile.read(8192):
process(chunk)
It doesn't belong to this paragraph though (I'm merely mentioning it)
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@giampaolo, I think that would be an excellent example to replace the one here! The clumsy 2-arg iter way of spelling that is
for chunk in iter((lambda: somefile.read(8192)), ""):
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Adding this now.