python / python/cpython

Cannot round-trip UCS-2 with unpaired surrogates using UTF-16 and surrogateescape

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docs topic-unicode
Dominant language
Python
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Description

Bug report

The following Python code throws a UnicodeEncodeError:

b'\xdc\xff'.decode('UTF-16BE', 'surrogateescape').encode('UTF-16', 'surrogateescape')

I would expect that it would return b'\xdc\xff' instead.

Your environment

  • CPython versions tested on: 3.10.4 from Fedora 35 repository
  • Operating system and architecture: Fedora 35 on x86-64

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Research direction

Start by running the reported UTF-16BE decode and UTF-16 encode snippet on the stated CPython version, then trace the relevant encoding and surrogateescape behavior. Done means the bytes b'\xdc\xff' round-trip without a UnicodeEncodeError, with behavior checked against the reported expectation.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
internationalization
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Clearly specified
Newbie friendliness
35/100

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