[Python-ideas] allow `lambda' to be spelled λ

[Neil Girdhar]

On Tue, Jul 19, 2016 at 7:21 AM Steven D'Aprano <steve at pearwood.info> wrote:

> On Mon, Jul 18, 2016 at 10:29:34PM -0700, Rustom Mody wrote:
>
> > There was this question on the python list a few days ago:
> > Subject: SyntaxError: Non-ASCII character
> [...]
> > I pointed out that the python2 error was more helpful (to my eyes) than
> > python3s
>
> And I pointed out how I thought the Python 3 error message could be
> improved, but the Python 2 error message was not very good.
>
>
> > Python3
> >
> > Traceback (most recent call last):
> >   File "<stdin>", line 1, in <module>
> >   File "/home/ariston/foo.py", line 31
> >     wf = wave.open(“test.wav”, “rb”)
> >                        ^
> > SyntaxError: invalid character in identifier
>
> It would be much more helpful if the caret lined up with the offending
> character. Better still, if the offending character was actually stated:
>
>     wf = wave.open(“test.wav”, “rb”)
>                    ^
> SyntaxError: invalid character '“' in identifier
>
>
> > Python2
> >
> > Traceback (most recent call last):
> >   File "<stdin>", line 1, in <module>
> >   File "foo.py", line 31
> > SyntaxError: Non-ASCII character '\xe2' in file foo.py on line 31, but no
> > encoding declared; see http://python.org/dev/peps/pep-0263/ for details
>
> As I pointed out earlier, this is less helpful. The line itself is not
> shown (although the line number is given), nor is the offending
> character. (Python 2 can't show the character because it doesn't know
> what it is -- it only knows the byte value, not the encoding.) But in
> the person's text editor, chances are they will see what looks to them
> like a perfectly reasonable character, and have no idea which is the
> byte \xe2.
>
>
>
> > IOW
> > 1. The lexer is internally (evidently from the error message) so
> > ASCII-oriented that any “unicode-junk” just defaults out to identifiers
> > (presumably comments are dealt with earlier) and then if that lexing
> action
> > fails it mistakenly pinpoints a wrong *identifier* rather than just an
> > impermissible character like python 2
>
> You seem to be jumping to a rather large conclusion here. Even if you
> are right that the lexer considers all otherwise-unexpected characters
> to be part of an identifier, why is that a problem?
>

It's a problem because those characters could never be part of an
identifier.  So it seems like a bug.


>
> I agree that it is mildly misleading to say
>
> invalid character '“' in identifier
>
> when “ is not part of an identifier:
>
> py> '“test'.isidentifier()
> False
>
> but I don't think you can jump from that to your conclusion that
> Python's unicode support is somewhat "wrongheaded". Surely a much
> simpler, less inflammatory response would be to say that this one
> specific error message could be improved?
>
> But... is it REALLY so bad? What if we wrote it like this instead:
>
> py> result = my§function(arg)
>   File "<stdin>", line 1
>     result = my§function(arg)
>                         ^
> SyntaxError: invalid character in identifier
>
> Isn't it more reasonable to consider that "my§function" looks like it is
> intended as an identifier, but it happens to have an illegal character
> in it?
>
> > combine that with
> > 2. matrix mult (@) Ok to emulate perl but not to go outside ASCII
>
> How does @ emulate Perl?
>
> As for your second part, about not going outside of ASCII, yes, that is
> official policy for Python operators, keywords and builtins.
>
>
> > makes it seem  (to me) python's unicode support is somewhat wrongheaded.
>
>
> --
> Steve
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