That PR seems to make \' and \" not special in general right? I think this is a more limited proposal, to only change the behavior when \ is at the end of a string, so the only behavior difference would never receiving the error "SyntaxError: EOL while scanning string literal" In which case there should be no backwards compatibility issue. Damian On Sat, May 28, 2022 at 12:20 PM Serhiy Storchaka wrote:

28.05.22 12:22, Steven D'Aprano пише:

...

Now that we have a new parser for CPython, can we fix the old gotcha that raw strings cannot end in a backslash?

Its an FAQ and has come up again on the bug tracker.

https://docs.python.org/3/faq/design.html#id26

https://github.com/python/cpython/issues/93314

I do not think that we can allow this, and it is not related to parser.

Few years ago I experimented with such change: https://github.com/python/cpython/pull/15217

You can see that it breaks even some stdlib code, and it will definitely break many third-party packages and examples. Technically we can do this, but the benefit is small in comparison with the cost.

_______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-leave@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/WWWRFQK4... Code of Conduct: http://python.org/psf/codeofconduct/

28.05.22 14:57, Damian Shaw пише:

That PR seems to make \' and \" not special in general right?

I think this is a more limited proposal, to only change the behavior when \ is at the end of a string, so the only behavior difference would never receiving the error "SyntaxError: EOL while scanning string literal"

In which case there should be no backwards compatibility issue.

How do you know that it is at the end of a string?

On 2022-05-28 16:03, MRAB wrote:

On 2022-05-28 13:17, Serhiy Storchaka wrote:

...

28.05.22 14:57, Damian Shaw пише:

...

That PR seems to make \' and \" not special in general right?

I think this is a more limited proposal, to only change the behavior when \ is at the end of a string, so the only behavior difference would never receiving the error "SyntaxError: EOL while scanning string literal"

In which case there should be no backwards compatibility issue.

How do you know that it is at the end of a string?

It would also affect triple-quoted strings.

Here's an idea: prefix rr ("really raw") that would treat all backslashes literally. Here's something I've just realised.

Names in Python are case-sensitive, yet the string prefixes are case-/insensitive/. Why?

On Sat, May 28, 2022 at 12:11 MRAB Names in Python are case-sensitive, yet the string prefixes are

case-/insensitive/.

Why?

IIRC we copied this from C for numeric suffixes (0l and 0L are the same; also hex digits and presumably 0XA == 0xa) and then copied that for string prefixes without thinking about it much. I guess it’s too late to change. —Guido -- --Guido (mobile)

My understanding was that was part of the question being asked, is it possible to know what with the new PEG parser? On Sat, May 28, 2022 at 1:25 PM Serhiy Storchaka wrote:

...

That PR seems to make \' and \" not special in general right?

I think this is a more limited proposal, to only change the behavior when \ is at the end of a string, so the only behavior difference would never receiving the error "SyntaxError: EOL while scanning string

28.05.22 14:57, Damian Shaw пише: literal"

...

In which case there should be no backwards compatibility issue.

How do you know that it is at the end of a string?

_______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-leave@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/BFGT3H57... Code of Conduct: http://python.org/psf/codeofconduct/

On 5/28/2022 7:57 AM, Damian Shaw wrote:

That PR seems to make \' and \" not special in general right?

I think this is a more limited proposal, to only change the behavior when \ is at the end of a string, so the only behavior difference would never receiving the error "SyntaxError: EOL while scanning string literal"

How would you know where the end of a string is? I think this is one of those things that's easy to look at for a human and figure out the intent, but not so easy for the lexer, without some heuristics and backtracking. If the trailing single quote is removed below, it changes from "backslash in the middle of a string" to "backslash at the end of a string, followed by an arbitrary expression. r'\' + "foo"' Eric

In which case there should be no backwards compatibility issue.

Damian

On Sat, May 28, 2022 at 12:20 PM Serhiy Storchaka wrote:

28.05.22 12:22, Steven D'Aprano пише: > Now that we have a new parser for CPython, can we fix the old gotcha > that raw strings cannot end in a backslash? > > Its an FAQ and has come up again on the bug tracker. > > https://docs.python.org/3/faq/design.html#id26 > > https://github.com/python/cpython/issues/93314

I do not think that we can allow this, and it is not related to parser.

Few years ago I experimented with such change: https://github.com/python/cpython/pull/15217

You can see that it breaks even some stdlib code, and it will definitely break many third-party packages and examples. Technically we can do this, but the benefit is small in comparison with the cost.

_______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-leave@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/WWWRFQK4... Code of Conduct: http://python.org/psf/codeofconduct/

_______________________________________________ Python-Dev mailing list --python-dev@python.org To unsubscribe send an email topython-dev-leave@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived athttps://mail.python.org/archives/list/python-dev@python.org/message/O3STZ54B... Code of Conduct:http://python.org/psf/codeofconduct/