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Misleading "Not an instance or subtype" error when assigning to property of frozen, slotted dataclass

type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

Status: Open.

#143969 In python/cpython;

· HalfWhitt opened on Jan 17, 2026

pathlib.Path.copy() hangs on FIFO pipes and loops infinitely on /dev/zero

type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

Status: Open.

#143968 In python/cpython;

· tonghuaroot opened on Jan 17, 2026

test_sys.test_objecttypes requires _datetime

testsTests in the Lib/test dirTests in the Lib/test dir

type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

Status: Open.

#143959 In python/cpython;

· youknowone opened on Jan 17, 2026

Asyncio debugging tools no longer work (<code>ps</code> and <code>pstree</code>)

3.15new features, bugs and security fixesnew features, bugs and security fixes

stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

topic-asyncio

type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

Status: Open.

#143952 In python/cpython;

· johnslavik opened on Jan 17, 2026

pycore_optimizer_types.h‎ needs to include stdbool.h

interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)

type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

Status: Open.

#143943 In python/cpython;

· jmroot opened on Jan 16, 2026

"RuntimeError: cannot reuse already awaited coroutine" since 08bc03ff (under PYTHONASYNCIODEBUG)

topic-asyncio

type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

Status: Open.

#143939 In python/cpython;

· vytas7 opened on Jan 16, 2026

AddressHeader problem when FriendlyName is improperly quoted and contains comma

pendingThe issue will be closed if no feedback is providedThe issue will be closed if no feedback is provided

type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

Status: Open.

#143938 In python/cpython;

· fostervbv opened on Jan 16, 2026

functools.singledispatch registration prioritizes the types of normal arguments before positional-only ones

3.13bugs and security fixesbugs and security fixes

3.14bugs and security fixesbugs and security fixes

3.15new features, bugs and security fixesnew features, bugs and security fixes

stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

Status: Open.

#143886 In python/cpython;

· pR0Ps opened on Jan 15, 2026

pdb: some expression results are printed to the debuggee stdout

stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

Status: Open.

#143874 In python/cpython;

· hyongtao-code opened on Jan 15, 2026

Python 3.14.1+ annotationlib regression: ForwardRef.__hash__ raises <code>TypeError: unhashable type: 'cell'</code>

3.14bugs and security fixesbugs and security fixes

3.15new features, bugs and security fixesnew features, bugs and security fixes

stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

topic-typing

type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

Status: Open.

#143831 In python/cpython;

· abhinand-c opened on Jan 14, 2026

Python IDLE Bug Report

pendingThe issue will be closed if no feedback is providedThe issue will be closed if no feedback is provided

topic-IDLE

type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

Status: Open.

#143822 In python/cpython;

· FaizanBinFiros opened on Jan 14, 2026

Bare <code>AttributeError</code> in <code>__getattr__</code> shows a garbled message with attribute suggestions

3.13bugs and security fixesbugs and security fixes

3.14bugs and security fixesbugs and security fixes

3.15new features, bugs and security fixesnew features, bugs and security fixes

stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

Status: Open.

#143811 In python/cpython;

· johnslavik opened on Jan 13, 2026