[Python-ideas] Updating PEP 315: do-while loops
larry at hastings.org
Sun Apr 26 04:35:15 CEST 2009
Raymond Hettinger wrote:
> 1) One approach uses the standard do-while name but keeps usual python
> style formatting by putting the condition at the top instead of the
> bottom where it is in C and Java:
I don't like the condition-at-the-top variants, with or without an
ellipsis. (At first glance anyway.)
> I haven't found any condition-at-the-end syntax that FeelsRight(tm).
> Probably everyone has an opinion on these, but I don't any think those
> could be called bike-shedding. The spelling does matter and hopefully
> the cleanest solution can be found.
I couldn't quite parse that, but I sure hope it meant "I'm up for yet
another round of discussion".
I propose we allow an "if" suffix to "break" and "continue". So I'd
spell your loop this way:
j = _int(random() * n)
continue if j in selected
This would require there be no implied "while True" for a "do" block.
If you hit the end of the "do" block, without following a continue,
you'd just leave the block. So this program would be legal:
print("well, that was pointless")
It would print two strings then exit. It would *not* loop. A little
unexpected I guess.
On the other hand this form gives a pleasing alternate spelling to
It also provides a dandy spelling for early-exit programming, without
nesting your ifs, or early return, or throwing an exception, or using
gotos which thankfully we don't have:
print("enter 1, then 2")
i = input()
break if i != '1'
i = input()
break if i != '2'
print("why do you mistreat me so? it was a simple request!")
Maybe it's just me, but I think that spelling and those semantics are
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