[Python-ideas] π = math.pi

[Steven D'Aprano]

On Fri, Jun 02, 2017 at 04:29:16PM -0700, Guido van Rossum wrote:

> Are those characters not considered Unicode letters? Maybe we could add
> their category to the allowed set?

They're not letters:

py> {unicodedata.category(c) for c in '∑√∫∞'}
{'Sm'}


That's Symbol, Math.

One problem is that the 'Sm' category includes a whole lot of 
mathematical symbols that we probably don't want in identifiers:

∴ ∣ ≈ ≒ ≝ ≫ ≮ ⊞  (plus MANY more variations on = < and > operators)

including some "Confusables":

∁ ∊ ∨ ∗ ∑ etc

C ε v * Σ

http://www.unicode.org/reports/tr39/

Of course a language can define identifiers however it likes, but I 
think it is relevant that the Unicode Consortium's default algorithm for 
determining an identifier excludes Sm.

http://www.unicode.org/reports/tr31/

I also disagree with Ivan that these symbols would be particularly 
useful in general, even for maths-heavy code, although I wouldn't say no 
to special casing ∞ (infinity) and maybe √ as a unary square root 
operator.



-- 
Steve