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GeezerVison is showing github.com — gh-158980: Fix StreamReader.decode() of the Windows cpXXX codecs by sricursion · Pull Request #158990 · python/cpython

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@sricursion

@sricursion sricursion commented Oct 7, 2026 •
edited by bedevere-app Bot
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codecs.StreamReader.read() calls self.decode(data, self.errors), but StreamReader.decode() of the codecs created by create_win32_code_page_codec() required a third positional argument, final. As a result, every read from the stream reader of a cpXXX codec that is implemented this way (for example codecs.getreader('cp20866') or codecs.StreamReaderWriter) raised TypeError. This was introduced in gh-123803, which added these codecs.

final now defaults to False, as in encodings.mbcs, so that an incomplete multibyte sequence is kept until the next read. The new test reads through cp20866 and cp20932, including one byte at a time, and is skipped when the code page is not present.

  • Issue: Windows cpXXX codecs: StreamReader raises TypeError (decode() missing 'final') #158980

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@sricursion
pythongh-158980: Fix StreamReader.decode() of the Windows cpXXX codecs
84f5208 
StreamReader.read() calls decode() with two arguments, but the
codecs created by create_win32_code_page_codec() required a third
one, final.  Make it optional, as in encodings.mbcs.
@python-cla-bot

python-cla-bot Bot commented Oct 7, 2026 •
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@bedevere-app bedevere-app Bot mentioned this pull request Oct 7, 2026
Windows cpXXX codecs: StreamReader raises TypeError (decode() missing 'final') #158980
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@bedevere-app bedevere-app Bot added the awaiting review label Oct 7, 2026
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@sricursion
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