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Groups > comp.lang.python > #109516
| From | Uri Even-Chen <uri@speedy.net> |
|---|---|
| Newsgroups | comp.lang.python |
| Subject | Re: Operator precedence problem |
| Date | 2016-06-05 19:05 +0300 |
| Message-ID | <mailman.9.1465142763.2306.python-list@python.org> (permalink) |
| References | <816c651a-d0ae-4e23-a5b2-72a8f7398468@googlegroups.com> <nj0kol$ps$1@ger.gmane.org> <mailman.5.1465112166.2306.python-list@python.org> <3ff71354-461a-4635-8d1a-c879243e39a8@googlegroups.com> <CAMQ2MsFfxF0wSL_y9tSFCoJ1BJ+GVqi2qJLTBzs7+BbGRjW3Bw@mail.gmail.com> |
My suggestion: Never write expressions, such as 2 ** 3 ** 2 or even 2 * 4
+ 5, without parentheses. Always add parentheses - 2 ** (3 ** 2) (or (2 **
3) **2) or (2 * 4) + 5 (or 2 * (4 + 5)).
*Uri Even-Chen*
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Email: uri@speedy.net
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On Sun, Jun 5, 2016 at 6:05 PM, ICT Ezy <ictezy@gmail.com> wrote:
> On Sunday, June 5, 2016 at 1:06:21 PM UTC+5:30, Peter Otten wrote:
> > ICT Ezy wrote:
> >
> > >>>> 2 ** 3 ** 2
> > > Answer is 512
> > > Why not 64?
> > > Order is right-left or left-right?
> >
> > ** is a special case:
> >
> > """
> > The power operator ** binds less tightly than an arithmetic or bitwise
> unary
> > operator on its right, that is, 2**-1 is 0.5.
> > """
> > https://docs.python.org/3.5/reference/expressions.html#id21
> >
> > Here's a little demo:
> >
> > $ cat arithdemo.py
> > class A:
> > def __init__(self, value):
> > self.value = str(value)
> > def __add__(self, other):
> > return self._op(other, "+")
> > def __pow__(self, other):
> > return self._op(other, "**")
> > def __repr__(self):
> > return self.value
> > def _op(self, other, op):
> > return A("({} {} {})".format(self.value, op, other.value))
> > $ python3 -i arithdemo.py
> > >>> A(1) + A(2) + A(3)
> > ((1 + 2) + 3)
> > >>> A(1) ** A(2) ** A(3)
> > (1 ** (2 ** 3))
>
> Thank you very much for your explanation
> --
> https://mail.python.org/mailman/listinfo/python-list
>
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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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