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Add π to the math module #103172

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@JosephSBoyle

Currently, the math module in CPython uses the identifier math.pi to represent the mathematical constant π. This breaks user expectations and violates the principle of least surprise.

To improve consistency and readability, I propose changing math.pi to math.π symbol throughout the module. The reasoning for this is threefold:

  1. This change will make the code more intuitive for mathematicians and scientists (at least 99%+ of python users) who are more used to seeing the π symbol, thus reducing cognitive load and allowing them to build more complicated research code.

  2. Python supports unicode characters such as π and we don't take advantage of this enough. We can use π, therefore we should.

  3. Nobody currently knows how to type π, if we make this change users will have to open the math module and copy and paste the variable name - which is a great way to increase the visibility of important module internals that users need to read.

Some would be tempted to create a math.pi alias to maintain backwards compatibility, but I think that would only encourage people to continue using the non-symbolic variable (bad), so I propose simply deleting math.pi entirely (users will get the hint!).

This is a pretty small change so I don't think a news entry is necessary, in fact I think not having a news entry would make this change a sort of cool Easter Egg that users can discover and enjoy!

Kind regards and happy April 1st,
Joe

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  1. sobolevn commented on Apr 1, 2023

    @sobolevn
    Member

    I think that 🥧 is a much better name! It looks tasty!

  2. kumaraditya303 commented on Apr 1, 2023

    @kumaraditya303
    Contributor

    Worth backporting to 2.7!

  3. rasputyashka commented on Apr 1, 2023

    @rasputyashka

    Yea, I was really surprised when realized that my keyboard has only π, but not "p" and "i". That's why i still don't use python when i do some rocket science.

  4. efahl commented on Apr 1, 2023

    @efahl
    Contributor

    Python supports unicode characters such as π and we don't take advantage of this enough. We can use π, therefore we should.

    I concur wholeheartedly with this. We should look for other opportunities to impose our will upon make life easier for all users, so suggest we use Σ to replace the 'sum' builtin.

  5. jschwar313 commented on Apr 1, 2023

    @jschwar313

    Sounds pretty irrational to me.

  6. flowerbug commented on Apr 1, 2023

    @flowerbug

    Everyone should write in the margins that using such a symbol is not reflecting the reality of the situation. As you are writing a finite symbol, but when you read and evaluate such a symbol your brain should never return. This is true of many such symbols where we fudge maths, e, 1/3, inf, etc.

  7. mrabarnett commented on Apr 1, 2023

    @mrabarnett

    And λ to replace 'lambda', of course.

    Plus 🐍 instead of 'Python'.

  8. rasputyashka commented on Apr 1, 2023

    @rasputyashka

    And λ to replace 'lambda', of course.

    Plus 🐍 instead of 'Python'.

    but we don't use "python" anywhere in the code. It's neither builtin or keyword.

  9. gvanrossum commented on Apr 1, 2023

    @gvanrossum
    Member

    Where’s the PR?

  10. added a commit that references this issue on Apr 1, 2023
  11. sfermigier commented on Apr 2, 2023

    @sfermigier

    On a more serious tone, the "empty set" character (“∅”, U+2205) should be usable to represent an empty set in Python. It currently is not allowed:

    Python 3.11.2 (main, Feb 16 2023, 02:51:42)
    >>> ∅ = set()
      File "<stdin>", line 1
        ∅ = set()
        ^
    SyntaxError: invalid character '∅' (U+2205)
    

    I believe it would be useful when working with set-theoretic code, in part because {} doesn't represent the empty set in Python.

  12. sfermigier commented on Apr 2, 2023

    @sfermigier

    Python supports unicode characters such as π and we don't take advantage of this enough. We can use π, therefore we should.

    I concur wholeheartedly with this. We should look for other opportunities to impose our will upon make life easier for all users, so suggest we use Σ to replace the 'sum' builtin.

    (Seriously) Note that currently the '∑' (U+2211) character is not allowed as an identifier in Python, so it isn't even doable (assuming it's a good idea):

    >>> ∑ = sum
      File "<stdin>", line 1
        ∑ = sum
        ^
    SyntaxError: invalid character '∑' (U+2211)
    
  13. AlexWaygood commented on Apr 2, 2023

    @AlexWaygood
    Member

    Alas! For it is no longer April 1, and what had yesterday seemed like a revelatory idea, now seems, uh, foolish.

    Thanks for the excellent April Fool's, @JosephSBoyle, it brightened my day :)

  14. efahl commented on Apr 2, 2023

    @efahl
    Contributor

    (Seriously) Note that currently the '∑' (U+2211) character is not allowed as an identifier in Python, so it isn't even doable (assuming it's a good idea):

    I didn't use 2211, I used Σ \u03a3, which is indeed valid as an identifier. Choose your homographs carefully.

  15. holdenweb commented on Apr 4, 2023

    @holdenweb
    Member

    I'd suggest this frivolity end immediately. Beware the ∏thon Secret Underground, who have spies out watching for this sort of @^&E$^^RVO^RVOP*&%^

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