[Python-Dev] Boundaries between numbers and identifiers

[Serhiy Storchaka]

26.04.18 22:02, Lukasz Langa пише:
>> On Apr 26, 2018, at 11:37 AM, Serhiy Storchaka <storchaka at gmail.com> wrote:
>>
>> 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.
> -1
>
> This would make Python 3.8 reject code due to stylistic preference. Code that it actually can unambiguously parse today.

Of course I don't propose to make it a syntax error in 3.8. It should 
first emit a SyntaxWarning and be converted into an error only in 3.10.

Or maybe first add a rule for this in PEP 8 and make it a syntax error 
in distant future, after all style checkers include it.

> I agree that a formatting style that omits whitespace between numerals and other tokens is terrible.  However, if you start downright rejecting it, you will likely punish the wrong people.  Users of third-party libraries will be met with random parsing errors in files they have no control over.  This is not helpful.
>
> And given BPO-33338 the standard library tokenizer would have to keep parsing those things as is.
>
> Making 0or[] working again is also not worth it since that's been broken since Python 2.6 and hopefully nobody is running Python 2.5-only code anymore.
>
> What we should instead is to make the standard library tokenizer reflect the behavior of Python 2.6+.

The behavior of the standard library tokenizer doesn't contradict rules. 
It is the most natural behavior of regex-based tokenizer. Actually the 
behavior of the building tokenizer can be incorrect. In any case 
accepting `1if 2else 3` and rejecting `0or[]` looks weird. They should 
use the same rule. "0or" and "2else" should be considered ambiguous or 
unambiguous in the same way.