On 2018-07-05 16:07, Victor Stinner wrote:
2018-07-05 15:14 GMT+02:00 Gustavo Carneiro <gjcarne...@gmail.com>:
I don't know if you're trying to propose something clever here, like "if (x
:= func()):" would assign to 'x' only inside the "then" body of the if, but
IMHO that would be a terrible idea:
I don't propose to change the PEP 572. I'm trying to explain to myself
where "if (var := expr): ..." would add anything to readers compared
to "var = expr; if var: ...". I know that var is still valid after the
if.
I'm not asking to raise a syntax error or even emit a linter warning
if var is used after the if. I'm just thinking loudly where the PEP
572 is appropriate.
IMHO the following code should not use assignement expression.
Good:
help = self._root_section.format_help()
if help:
help = self._long_break_matcher.sub('\n\n', help)
help = help.strip('\n') + '\n'
return help
Bad?
if (help := self._root_section.format_help()):
help = self._long_break_matcher.sub('\n\n', help)
help = help.strip('\n') + '\n'
return help
IHMO using "help :=" here would send the wrong signal to the reader:
as if help is not going to be used after the if, whereas it's the case
("return help").
I think it's OK if it's:
Do something, and if that succeeded, act on it.
but not if it's:
Do something, but if that failed, do something else.
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