Path: csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail
From: Terry Reedy <tjreedy@udel.edu>
Newsgroups: comp.lang.python
Subject: Re: Question about math.pi is mutable
Date: Fri, 6 Nov 2015 20:49:17 -0500
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On 11/6/2015 5:26 PM, Thomas 'PointedEars' Lahn wrote:
> Bartc wrote:

>> import math
>>
>> math.pi=3D0
>>
>> print (math.pi)
>>
>> In Python, presumably 'pi' is just another variable, and variables can=

>> be written to.
>
> =E2=80=9Cpi=E2=80=9D is the name of an attribute of the module object r=
eferred to by =E2=80=9Cmath=E2=80=9D.
>
>> (Perhaps math.pi would be better off as a function.)
>
> Perhaps not.  Calling a function includes an overhead that one does not=
 want
> in already costly floating-point calculations.
>
> In my opinion, mathematical constants should be implemented as constant=
s
> (non-overwritable, non-deletable, throwing exceptions when attempting t=
o do
> either) but apparently the authors of math.py disagree.

One of multiple discussions of the 'constants' idea.
bugs.python.org/issue1465406
It is mostly about speed.

--=20
Terry Jan Reedy