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Recent changes to CPython's grammar and PEG parser, PEP-617 #2759
Description
Feature
CPython3.9+ support some new grammar rules, like () around with expression:
» python3.9 --version
Python 3.9.4
» python3.9
Python 3.9.4 (default, Apr 5 2021, 01:47:16)
[Clang 11.0.0 (clang-1100.0.33.17)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> with (open('a') as f):
... print(f)
...
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
FileNotFoundError: [Errno 2] No such file or directory: 'a'But, RustPython does not support it:
I think that the root of this problem is that new PEG parser is not supported: https://github.com/RustPython/RustPython/blob/master/parser/src/python.lalrpop
Python Documentation
Reacted by seungha-kim
Activity
DimitrisJim commentedon Jul 29, 2021
Yup, the project is currently targeting 3.8 so this shouldn't come as a surprise. Hopefully, at some point in the future, 3.9 will be the new goal and using a PEG parser will probably be needed.
sobolevn commentedon Jul 29, 2021
Then, I guess we can change this line in the README, because
3.9>=3.8🙂sobolevn commentedon Jul 29, 2021
Also: #2417
youknowone commentedon Aug 4, 2021
I think we are practically not pinning a target. Any patch for 3.9+ features will be appreciated.
fanninpm commentedon Aug 10, 2021
I believe 3.8 is the absolute minimum because it's referenced in
.github/workflows/ci.yaml.youknowone commentedon Aug 10, 2021
we just can change it to 3.9 once we feel it is more convenient. that happened a few times.
youknowone commentedon Aug 11, 2021
#2831
sobolevn commentedon Aug 11, 2021
Related https://github.com/zsol/LibCST/blob/parser/native/libcst_parser/src/grammar.rs
youknowone commentedon Dec 10, 2022
We'd better to rewrite our parser based on same parser definition with CPython.
youknowone commentedon Dec 12, 2022
see also: astral-sh/ruff#286
youknowone commentedon Oct 6, 2026
Parenthesized `with` (PEP 617) works on current main, e.g. `with (open("/dev/null") as f):` and multi-context parenthesized `with`. The parser is no longer the old LL parser. Closing.
— commented by Grok 4.6