On Tue, Apr 13, 2021 at 12:55 PM Serhiy Storchaka <storch...@gmail.com>
wrote:
> 26.04.18 21:37, Serhiy Storchaka пише:
> > In Python 2.5 `0or[]` was accepted by the Python parser. It became an
> > error in 2.6 because "0o" became recognizing as an incomplete octal
> > number. `1or[]` still is accepted.
> >
> > On other hand, `1if 2else 3` is accepted despites the fact that "2e" can
> > be recognized as an incomplete floating point number. In this case the
> > tokenizer pushes "e" back and returns "2".
> >
> > Shouldn't it do the same with "0o"? It is possible to make `0or[]` be
> > parseable again. Python implementation is able to tokenize this example:
> >
> > $ echo '0or[]' | ./python -m tokenize
> > 1,0-1,1: NUMBER '0'
> > 1,1-1,3: NAME 'or'
> > 1,3-1,4: OP '['
> > 1,4-1,5: OP ']'
> > 1,5-1,6: NEWLINE '\n'
> > 2,0-2,0: ENDMARKER ''
> >
> > On other hand, all these examples look weird. There is an assymmetry:
> > `1or 2` is a valid syntax, but `1 or2` is not. It is hard to recognize
> > visually the boundary between a number and the following identifier or
> > keyword, especially if numbers can contain letters ("b", "e", "j", "o",
> > "x") and underscores, and identifiers can contain digits. On both sides
> > of the boundary can be letters, digits, and underscores.
> >
> > I propose to change the Python syntax by adding a requirement that there
> > should be a whitespace or delimiter between a numeric literal and the
> > following keyword.
> >
>
> New example was found recently (see https://bugs.python.org/issue43833).
>
> >>> [0x1for x in (1,2)]
> [31]
>
> It is parsed as [0x1f or x in (1,2)] instead of [0x1 for x in (1,2)].
>
> Since this code is clearly ambiguous, it makes more sense to emit a
> SyntaxWarning if there is no space between number and identifier.
>
I would totally make that a SyntaxError, and backwards compatibility be
damned.
--
--Guido van Rossum (python.org/~guido)
*Pronouns: he/him **(why is my pronoun here?)*
<http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
_______________________________________________
Python-Dev mailing list -- python-dev@python.org
To unsubscribe send an email to python-dev-le...@python.org
https://mail.python.org/mailman3/lists/python-dev.python.org/
Message archived at
https://mail.python.org/archives/list/python-dev@python.org/message/OU3USHVMXZJD4SA3FJGQQVQYAORHY5BM/
Code of Conduct: http://python.org/psf/codeofconduct/
