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Groups > comp.lang.python > #109580
| From | Peter Otten <__peter__@web.de> |
|---|---|
| Newsgroups | comp.lang.python |
| Subject | Re: Operator precedence problem |
| Date | 2016-06-06 18:38 +0200 |
| Organization | None |
| Message-ID | <mailman.42.1465231123.2306.python-list@python.org> (permalink) |
| References | (6 earlier) <2a577a90-3a39-4d8f-90fa-4a00fd4f06a3@googlegroups.com> <1465221421.1069788.629246361.60094337@webmail.messagingengine.com> <mailman.37.1465221424.2306.python-list@python.org> <87inxmmm67.fsf@elektro.pacujo.net> <nj48u8$h3f$1@ger.gmane.org> |
Marko Rauhamaa wrote:
> Random832 <random832@fastmail.com>:
>
>> Sure, it's obvious to _me_ that << and >> have higher precedence than &
>> and |, and that "and" has a higher precedence than "or", but can I
>> assume the other people know this?
>
> No need to assume. Just read the spec:
>
> lambda Lambda expression
> if – else Conditional expression
> or Boolean OR
> and Boolean AND
> not x Boolean NOT
> in, not in, is, is not, <, <=, >, >=, !=, ==
> Comparisons, including membership tests and identity
> tests
> | Bitwise OR
> ^ Bitwise XOR
> & Bitwise AND
> <<, >> Shifts
> +, - Addition and subtraction
> *, @, /, //, % Multiplication, matrix multiplication division,
> remainder [5]
> +x, -x, ~x Positive, negative, bitwise NOT
> ** Exponentiation [6]
> await x Await expression
> x[index], x[index:index], x(arguments...), x.attribute
> Subscription, slicing, call, attribute reference
> (expressions...), [expressions...], {key: value...}, {expressions...}
> Binding or tuple display, list display, dictionary
> display, set display
>
> <URL: https://docs.python.org/3/reference/expressions.html#operat
> or-precedence>
>
>> [To keep this on-topic, let's assume that this discussion has a goal of
>> getting something along the lines of "always/sometimes/never use
>> "unnecessary" parentheses" into PEP7/PEP8. Speaking of, did you know
>> that C has lower precedence for the bitwise operators &^| than for
>> comparisons? That was something that tripped me up for a very long time
>> and undermined my confidence as to other aspects of the bitwise
>> operators]
>
> Yes, I happened to know that. Python's the same way.
It's not. From the page you linked to:
"""
Unlike C, all comparison operations in Python have the same priority, which
is lower than that of any arithmetic, shifting or bitwise operation.
"""
> However, no need to memorize. It's all there in the spec. Same as with
> stdlib functions. Keep checking the spec.
Nah, I usually try it in the interactive interpreter:
$ python3 -c 'print(1 < 3 & 2)'
True
$ echo 'main() { printf("%d\n", 1 < 3 & 2); }' | tcc -run -
0
(tcc invocation courtesy of google/stackoverflow)
> You *can* assume other people have read the spec. Even more importantly,
> you can assume the Python interpreter complies with the spec.
Back to comp.lang.python | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Operator precedence problem ICT Ezy <ictezy@gmail.com> - 2016-06-04 23:53 -0700
Re: Operator precedence problem Peter Otten <__peter__@web.de> - 2016-06-05 09:35 +0200
Re: Operator precedence problem ICT Ezy <ictezy@gmail.com> - 2016-06-05 08:05 -0700
Re: Operator precedence problem Uri Even-Chen <uri@speedy.net> - 2016-06-05 19:05 +0300
Re: Operator precedence problem ICT Ezy <ictezy@gmail.com> - 2016-06-05 20:24 -0700
Re: Operator precedence problem Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-06-05 22:46 -0700
Re: Operator precedence problem Random832 <random832@fastmail.com> - 2016-06-06 09:57 -0400
Re: Operator precedence problem Marko Rauhamaa <marko@pacujo.net> - 2016-06-06 17:22 +0300
Re: Operator precedence problem Random832 <random832@fastmail.com> - 2016-06-06 10:35 -0400
Re: Operator precedence problem Marko Rauhamaa <marko@pacujo.net> - 2016-06-06 17:55 +0300
Re: Operator precedence problem Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2016-06-06 15:03 +0000
Re: Operator precedence problem Marko Rauhamaa <marko@pacujo.net> - 2016-06-06 18:22 +0300
Re: Operator precedence problem Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2016-06-06 15:27 +0000
Re: Operator precedence problem Chris Angelico <rosuav@gmail.com> - 2016-06-07 01:57 +1000
Re: Operator precedence problem Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2016-06-06 16:05 +0000
Re: Operator precedence problem Chris Angelico <rosuav@gmail.com> - 2016-06-07 02:21 +1000
Re: Operator precedence problem Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2016-06-06 17:02 +0000
Re: Operator precedence problem Grant Edwards <grant.b.edwards@gmail.com> - 2016-06-06 16:51 +0000
Re: Operator precedence problem Peter Otten <__peter__@web.de> - 2016-06-06 18:38 +0200
Re: Operator precedence problem Steven D'Aprano <steve@pearwood.info> - 2016-06-07 03:07 +1000
Re: Operator precedence problem Random832 <random832@fastmail.com> - 2016-06-06 14:44 -0400
Re: Operator precedence problem Marko Rauhamaa <marko@pacujo.net> - 2016-06-06 21:49 +0300
Re: Operator precedence problem MRAB <python@mrabarnett.plus.com> - 2016-06-06 20:17 +0100
Re: Operator precedence problem Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-06-07 11:27 +1200
Re: Operator precedence problem Rustom Mody <rustompmody@gmail.com> - 2016-06-06 10:14 -0700
Re: Operator precedence problem Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-06-06 21:09 +0100
Re: Operator precedence problem Michael Torrie <torriem@gmail.com> - 2016-06-05 17:47 -0600
Re: Operator precedence problem ICT Ezy <ictezy@gmail.com> - 2016-06-05 20:23 -0700
Re: Operator precedence problem Chris Angelico <rosuav@gmail.com> - 2016-06-06 02:24 +1000
Re: Operator precedence problem Peter Pearson <pkpearson@nowhere.invalid> - 2016-06-06 16:58 +0000
Re: Operator precedence problem Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-06-07 11:21 +1200
Re: Operator precedence problem Random832 <random832@fastmail.com> - 2016-06-05 13:19 -0400
Re: Operator precedence problem ICT Ezy <ictezy@gmail.com> - 2016-06-05 20:23 -0700
Re: Operator precedence problem Gary Herron <gherron@digipen.edu> - 2016-06-05 00:04 -0700
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