Unicode identifiers in Python?

Question

I want to build a Python function that calculates,

and would like to name my summation function Σ. In a similar fashion, would like to use Π for product, and so on. I was wondering if there was a way to name a python function in this fashion?

def Σ (..):
 ..
 ..

That is, does Python support unicode identifiers, and if so, could someone provide an example for it?

Thanks!

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Original motivation for this was a piece of Clojure code I saw today that looks like,

(defn entropy [X]
      (* -1 (Σ [i X] (* (p i) (log (p i))))))

where Σ is a macro defined as,

(defmacro Σ
    ... )

and I thought that was pretty cool.

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BTW, to address a couple of comments about readability - with a lot of stats/ML code for instance, being able to compose operations with symbols would be really helpful. (Especially for really complex integrals et al)

φ(z) = ∫(N(x|0,1,1), -∞, z)

vs

Phi(z) = integral(N(x|0,1,1), -inf, z)

or even just the lambda character for lambda()!

Answer 1

(I think it’s pretty cool too, that might mean we’re geeks.)

You’re fine to do this with the code you have above in Python 3. (It works in my Python 3.1 interpreter at least.) See:

• http://docs.python.org/py3k/reference/lexical_analysis.html#identifiers
• http://www.python.org/dev/peps/pep-3131/

But in Python 2, identifiers can only be ASCII letters, numbers and underscores.

• http://docs.python.org/reference/lexical_analysis.html#identifiers