gh-98401: Invalid escape sequences emits SyntaxWarning by vstinner · Pull Request #99011 · python/cpython (original) (raw)

A backslash-character pair that is not a valid escape sequence now generates a SyntaxWarning, instead of DeprecationWarning. For example, re.compile("\d+.\d+") now emits a SyntaxWarning ("\d" is an invalid escape sequence), use raw strings for regular expression: re.compile(r"\d+.\d+"). In a future Python version, SyntaxError will eventually be raised, instead of SyntaxWarning.

Octal escapes with value larger than 0o377 (ex: "\477"), deprecated in Python 3.11, now produce a SyntaxWarning, instead of DeprecationWarning. In a future Python version they will be eventually a SyntaxError.

codecs.escape_decode() and codecs.unicode_escape_decode() are left unchanged: they still emit DeprecationWarning.

• The parser only emits SyntaxWarning for Python 3.12 (feature version), and still emits DeprecationWarning on older Python versions.
• Fix SyntaxWarning by using raw strings in Tools/c-analyzer/ and wasm_build.py.
• Issue: Reject invalid escape sequences (and octal escape sequences) in bytes and Unicode strings #98401