[Python-ideas] Visually confusable unicode characters in identifiers

[Guido van Rossum]

On Mon, Oct 1, 2012 at 1:26 PM, Oscar Benjamin
<oscar.j.benjamin at gmail.com> wrote:
> On 1 October 2012 20:33, Mathias Panzenböck
> <grosser.meister.morti at gmx.net> wrote:
>>
>> On 10/01/2012 07:48 PM, Georg Brandl wrote:
>>>
>>> On 10/01/2012 07:02 PM, Mathias Panzenböck wrote:
>>>>
>>>> On 10/01/2012 06:43 PM, Robert Kern wrote:
>>>>>
>>>>> On 10/1/12 5:07 PM, Mathias Panzenböck wrote:
>>>>>>
>>>>>> I still don't understand why unicode characters are allowed at all in identifier
>>>>>> names. Is the reason for this written down somewhere?
>>>>>
>>>>>
>>>>> http://www.python.org/dev/peps/pep-3131/#rationale
>>>>>
>>>>
>>>> But the Python keywords and more importantly the documentation is English. Don't you need to be able
>>>> to speak/write English in order to code Python anyway? And if you keep you code+comments English you
>>>> can access a much larger developer pool (all developers who speak English should by my hypothesis be
>>>> a superset of all developers who speak a certain language).
>>>
>>>
>>> Please; the PEP has been discussed quite a lot when it was proposed,
>>> and believe me, yours is not an unfamiliar argument :)  You're about
>>> 5 years late.
>>>
>>> Georg
>>>
>>
>> I didn't want to start a discussion. I just wanted to know why one would implement such a language feature. Guido's answer cleared it up for me, thanks. I can see the purpose in an educational setting (not in production code of anything a little bit bigger).
>
> Non-ascii identifiers have other possible uses. I'll repost the case
> that started this discussion on python-tutor (attached in case it
> doesn't display):
>
> '''
> #!/usr/bin/env python3
> # -*- encoding: utf-8 -*-
>
> # Parameters
> α = 1
> β = 0.1
> γ = 1.5
> δ = 0.075
>
> # Initial conditions
> xₒ = 10
> yₒ = 5
> Zₒ = xₒ, yₒ
>
> # Solution parameters
> tₒ = 0
> Δt = 0.001
> T = 10
>
> # Lotka-Volterra derivative
> def f(Z, t):
>     x, y = Z
>     ẋ = x * (α - β*y)
>     ẏ = -y * (γ - δ*x)
>     return ẋ, ẏ
>
> # Accumulate results from Euler stepper
> tᵢ = tₒ
> Zᵢ = Zₒ
> Zₜ, t = [], []
> while tᵢ <= tₒ + T:
>     Zₜ.append(Zᵢ)
>     t.append(tᵢ)
>     Zᵢ = [Zᵢⱼ+ Δt*Żᵢⱼ for Zᵢⱼ, Żᵢⱼ in zip(Zᵢ, f(Zᵢ, tᵢ))]
>     tᵢ += Δt
>
> # Output since I don't have plotting libraries in Python 3
> print('t', 'x', 'y')
> for tᵢ, (xᵢ, yᵢ) in zip(t, Zₜ):
>     print(tᵢ, xᵢ, yᵢ)
> '''

Those examples would be a lot more compelling if there was an
acceptable way to input those characters. Maybe we could support some
kind of input method that enabled LaTeX style math notation as used by
scientists for writing equations in papers?

-- 
--Guido van Rossum (python.org/~guido)