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Title: bpo-35224: PEP 572 Implementation by emilyemorehouse · Pull Request #10497 · python/cpython · GitHub

Open Graph Title: bpo-35224: PEP 572 Implementation by emilyemorehouse · Pull Request #10497 · python/cpython

X Title: bpo-35224: PEP 572 Implementation by emilyemorehouse · Pull Request #10497 · python/cpython

Description: This is the implementation of PEP 572. It has been few a couple of rounds of refactoring per my and Guido's review, but is now ready for a more thorough review from others. The only TODO items before merging are: News entry Thorough reviews Additional Notes The new test cases of note can be explicitly run using: ./python.exe -m test -v test_parser -v test_named_expressions ./python.exe -m test -v test_parser -v test_parser ./python.exe -m test -v test_parser -v test_tokenize Please note the following caveats and future tasks. These items are NOT blocking reviews or merging, but are here as FYIs if they come up in review: Must decide upon cleaner implementation of disallowing expressions such as ((a) := 10), or to continuing allowing this. The current, and know-to-be-imperfect, implementation was introduced here. This change has been reverted and deferred There are a few minor differences between how the implementation functions versus the spec in the PEP. See below for more information. Documentation updates will come in a separate PR Differences between the PEP spec and implementation From the "Scope of the target" section of the PEP, there are two cases that should raise a TargetScopeError: when an assignment expression is used in a comprehension inside a class body or for special cases in comprehensions. Invalid examples for the latter include: [i := i+1 for i in range(5)] [[(j := j) for i in range(5)] for j in range(5)] [i := 0 for i, j in stuff] [i+1 for i in i := stuff] However, the following work in the implementation,though the PEP states they should be invalid: >>> [i := i+1 for i in range(5)] [1, 2, 3, 4, 5] >>> i 5 >>> [i := 0 for i, j in [(1, 2)]] [0] The following does not work in the implementation (as desired), but does not throw a TargetScopeError as defined in the PEP: >>> [i+1 for i in i := range(5)] File "", line 1 [i+1 for i in i := range(5)] ^ SyntaxError: invalid syntax https://bugs.python.org/issue35224

Open Graph Description: This is the implementation of PEP 572. It has been few a couple of rounds of refactoring per my and Guido's review, but is now ready for a more thorough review from others. The only TODO items...

X Description: This is the implementation of PEP 572. It has been few a couple of rounds of refactoring per my and Guido's review, but is now ready for a more thorough review from others. The only TODO i...

Opengraph URL: https://github.com/python/cpython/pull/10497

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