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Groups > comp.lang.python > #101846
| From | Peter Otten <__peter__@web.de> |
|---|---|
| Newsgroups | comp.lang.python |
| Subject | Re: "x == None" vs "x is None" |
| Date | 2016-01-17 12:26 +0100 |
| Organization | None |
| Message-ID | <mailman.58.1453030018.15297.python-list@python.org> (permalink) |
| References | <n7fo7q$dso$1@news2.informatik.uni-stuttgart.de> <mailman.57.1453025729.15297.python-list@python.org> <n7fshb$f36$1@news2.informatik.uni-stuttgart.de> |
Ulli Horlacher wrote: > Chris Angelico <rosuav@gmail.com> wrote: >> On Sun, Jan 17, 2016 at 8:51 PM, Ulli Horlacher >> <framstag@rus.uni-stuttgart.de> wrote: >> > I have seen at several places "x == None" and "x is None" within >> > if-statements. >> > What is the difference? >> > Which term should I prefer and why? >> >> tl;dr: Prefer "x is None" as a check. > > And for the negation? > "if not x is None" or "if x is not None" > > I have seen the last one several times, but i do not understand it, > because: > >>>> x=0 >>>> x is not None > True >>>> not None > True >>>> x is True > False - "is" has higher precedence than "not" - "is not" is an operator in its own right. So the evaluation is not (x is None) x (is not) None https://docs.python.org/dev/library/stdtypes.html#comparisons https://docs.python.org/dev/reference/expressions.html#operator-precedence
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"x == None" vs "x is None" Ulli Horlacher <framstag@rus.uni-stuttgart.de> - 2016-01-17 09:51 +0000
Re: "x == None" vs "x is None" Chris Angelico <rosuav@gmail.com> - 2016-01-17 21:15 +1100
Re: "x == None" vs "x is None" Ulli Horlacher <framstag@rus.uni-stuttgart.de> - 2016-01-17 11:05 +0000
Re: "x == None" vs "x is None" Peter Otten <__peter__@web.de> - 2016-01-17 12:26 +0100
Re: "x == None" vs "x is None" Chris Angelico <rosuav@gmail.com> - 2016-01-17 22:29 +1100
Re: "x == None" vs "x is None" <paul.hermeneutic@gmail.com> - 2016-01-17 11:01 -0700
Re: "x == None" vs "x is None" Random832 <random832@fastmail.com> - 2016-01-17 16:33 -0500
Re: "x == None" vs "x is None" Chris Angelico <rosuav@gmail.com> - 2016-01-18 08:38 +1100
Re: "x == None" vs "x is None" Ben Finney <ben+python@benfinney.id.au> - 2016-01-18 13:46 +1100
Re: "x == None" vs "x is None" fernando junior <fernandojr.ifcg@live.com> - 2016-01-19 14:20 -0800
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