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/

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

-1

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.

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.

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.

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

Can you prove that?

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. :)

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.

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

> http://tauday.com/

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

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

https://github.com/search?q=%22TAU+%3D+2+%2A+Math.PI%22&type=Code
https://github.com/search?q=%22TAU+%3D+PI+*+2%22&type=Code

Following-up sbaird's comment, I must point out that those aren't Python-specific results. Filtering them by appending &l=python to the urls yields:
- "TAU = 2 * Math.PI": 6
- "TAU = 2*Math.PI": 2
- "TAU=2*Math.PI": 0
- "TAU = Math.PI * 2": 0
- "TAU = Math.PI*2": 2
- "TAU=Math.PI*2": 1
(total: 11)

- "TAU = 2 * PI": 9
- "TAU = 2*PI": 12
- "TAU=2*PI": 0
- "TAU = PI * 2": 2
- "TAU = PI*2": 0
- "TAU=PI*2": 0
(total: 23)

Then again, the results for all languages are still helpful to estimate the overall adoption of the notation in code, and indeed the global usage of these patterns (in github only) is in the hundreds.

Also, it's worth taking a look at the usage of the twopi constant, which is already defined in several languages (http://en.wikipedia.org/w/index.php?oldid=509096802#Support_in_programming_languages), and has been manually defined in python quite often, proving its usefulness:

- https://github.com/search?l=python&q=twopi&type=Code (~2k results in python, and ~58k overall)
- https://github.com/search?l=python&q=two_pi&type=Code (~200 results in python, ~23k overall)