Add math.tau

[ncoghlan]

BPO	12345
Nosy	@tim-one, @birkenfeld, @rhettinger, @pfalcon, @mdickinson, @ncoghlan, @abalkin, @vstinner, @benjaminp, @merwok, @asmeurer, @serhiy-storchaka, @vedgar, @Shredder13, @lisroach, @AraHaan
PRs	[3.6] bpo-34901 - add isolated (-I) flag to sys.flags (GH-9708) #9755
Files	tau.diff tau2.diff tau3.diff tau4.diff

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/gvanrossum'
closed_at = <Date 2016-08-15.16:16:35.929>
created_at = <Date 2011-06-16.03:10:29.721>
labels = ['easy', 'type-feature']
title = 'Add math.tau'
updated_at = <Date 2018-10-08.22:18:18.242>
user = 'https://github.com/ncoghlan'

bugs.python.org fields:

activity = <Date 2018-10-08.22:18:18.242>
actor = 'danishprakash'
assignee = 'gvanrossum'
closed = True
closed_date = <Date 2016-08-15.16:16:35.929>
closer = 'gvanrossum'
components = []
creation = <Date 2011-06-16.03:10:29.721>
creator = 'ncoghlan'
dependencies = []
files = ['44063', '44065', '44080', '44111']
hgrepos = []
issue_num = 12345
keywords = ['patch', 'easy']
message_count = 63.0
messages = ['138412', '138414', '138416', '138419', '138421', '138422', '138423', '138431', '138548', '138551', '138553', '139338', '183004', '183198', '272287', '272299', '272301', '272304', '272319', '272325', '272373', '272374', '272375', '272376', '272377', '272422', '272457', '272465', '272467', '272469', '272470', '272472', '272473', '272476', '272478', '272483', '272484', '272485', '272487', '272493', '272505', '272507', '272509', '272533', '272555', '272561', '272566', '272592', '272598', '272601', '272617', '272618', '272627', '272671', '272679', '272682', '272714', '272770', '272775', '272777', '272802', '313664', '313668']
nosy_count = 20.0
nosy_names = ['tim.peters', 'georg.brandl', 'rhettinger', 'pfalcon', 'mark.dickinson', 'ncoghlan', 'belopolsky', 'vstinner', 'benjamin.peterson', 'stutzbach', 'eric.araujo', 'Aaron.Meurer', 'python-dev', 'serhiy.storchaka', 'waldir', 'xcombelle', 'veky', 'Nofar Schnider', 'lisroach', 'Decorater']
pr_nums = ['9755']
priority = 'normal'
resolution = 'fixed'
stage = 'commit review'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue12345'
versions = ['Python 3.6']

[ncoghlan]

I'd like to add a new constant to the math module:

  tau = 2*math.pi

Rather than repeating all the reasons for why tau makes more sense than pi as the fundamental circle constant, I'll just refer interested readers to http://tauday.com/

[benjaminp]

Perhaps we should wait until \tau gains popularity larger than some impassioned physicist. \tau has been used to represent the golden ratio longer.

[rhettinger]

-1

[ncoghlan]

The golden ratio is more commonly denoted with phi (although tau does get used sometimes).

Popularity isn't the point though, it's the fact that tau *makes geometric sense* in ways that 2*pi doesn't.

[vstinner]

I like this issue number, but I don't think that Python needs this new constant: it's trivial to add it to your own project. We have pi and e, it's enough. If we begin to add a new constant, others will ask to add much more constants, and there are million of other constants (useful or not). You may want to create a library of some other common constants. You can use float.fromhex() to have a good accuracy.

[pitrou]

Nick, you just have to write: tau = 2 * math.pi
and you're done.

there are million of other constants

Actually, I've heard there are an infinity of them.

[vstinner]

Actually, I've heard there are an infinity of them.

Can you prove that?

[benjaminp]

2011/6/16 STINNER Victor <report@bugs.python.org>:

STINNER Victor <victor.stinner@haypocalc.com> added the comment:

> Actually, I've heard there are an infinity of them.

Can you prove that?

Don't have to. Axiom of infinity. :)

[stutzbach]

On Wed, Jun 15, 2011 at 8:10 PM, Nick Coghlan <report@bugs.python.org>wrote:

I'd like to add a new constant to the math module:

tau = 2*math.pi

Rather than repeating all the reasons for why tau makes more sense than pi
as the fundamental circle constant, I'll just refer interested readers to
http://tauday.com/

(The following is best if read aloud using your best pirate impression)

I'd rather name the new constant "matey". Then we have:

The circumference of a circle is: r matey
The area of a circle is: one-quarter r r matey
etc.

[mdickinson]

Not to mention d(area of circle of radius r) = r dr matey.

[birkenfeld]

http://tauday.com/

And I thought putting "dx" directly next to the integral sign was audacious...

[gvanrossum]

Uh, not until I've seen a lot more evidence that people are habitually writing "TAU = 2 * math.pi" in their programs...