Well, I finally ran into a Python Unicode problem, sort of
Rustom Mody
rustompmody at gmail.com
Sun Jul 3 03:26:55 EDT 2016
On Sunday, July 3, 2016 at 12:29:14 PM UTC+5:30, John Ladasky wrote:
> A while back, I shared my love for using Greek letters as variable names in my Python (3.4) code -- when, and only when, they are warranted for improved readability. For example, I like to see the following:
>
>
> from math import pi as π
>
> c = 2 * π * r
>
>
> When I am copying mathematical formulas from publications, and Greek letters are used in that publication, I prefer to follow the text exactly as written.
>
> Up until today, every character I've tried has been accepted by the Python interpreter as a legitimate character for inclusion in a variable name. Now I'm copying a formula which defines a gradient. The nabla symbol (∇) is used in the naming of gradients. Python isn't having it. The interpreter throws a "SyntaxError: invalid character in identifier" when it encounters the ∇.
>
> I am now wondering what constitutes a valid character for an identifier, and how they were chosen. Obviously, the Western alphabet and standard Greek letters work. I just tried a few very weird characters from the Latin Extended range, and some Cyrillic characters. These are also fine.
https://docs.python.org/3.5/reference/lexical_analysis.html
points to
https://www.dcl.hpi.uni-potsdam.de/home/loewis/table-3131.html
Quite hardwired
>
> A philosophical question. Why should any character be excluded from a variable name, besides the fact that it might also be an operator?
>
> This might be a problem I can solve, I'm not sure. Is there a file that the Python interpreter refers to which defines the accepted variable name characters? Perhaps I could just add ∇.
You need to try something like
>>> import unicodedata as ud
>>> ud.category("∇")
'Sm'
>>> ud.category("A")
'Lu'
>>> ud.category("π")
'Ll'
>>> ud.category("a")
'Ll'
followed by figuring out why/what etc from (say)
https://en.wikipedia.org/wiki/Unicode_character_property
This is the way it IS
Not saying it SHOULD BE…
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