pypi / pywinpty

pywinpty

What changed in pywinpty 2 to 3, from its official release notes, upgrade guides and advisories. Sources checked 2026-10-29.

8 breaking1 new APIs and options2 performance3 tooling8 fixes and other

See which of these apply to your code, ranked, in your agent:

npx @unstale/cli init

pywinpty 317 changes

PTY.iseof() now returns True once output is drained. Read loops that relied on it always returning False may behave differently and may need their condition inverted.
3.1.2release notes
PTY.write() no longer returns 0 for payloads the child received in full.
3.1.1release notes
Python 3.13t wheels are no longer built because PyO3 dropped support for that experimental version.
3.1.0release notes
The supported Python requirement is now >=3.10; Python 3.9 is no longer supported.
3.0.4release notes
read no longer accepts num_bytes and returns all available bytes in the stream, delegating buffering to downstream consumers.
3.0.0release notes

pywinpty supports async compatibility on ConPTY through the latest winpty-rs release.
3.0.0release notes

Reading from a pseudoterminal now takes tenths of microseconds rather than 100ms as previously.
3.0.0release notes

Wheels are now built for Python 3.15 and 3.15t on Windows x64 and ARM64.
3.1.0release notes
ARM64 wheel publishing is introduced, making pywinpty wheels available for ARM64.
3.0.3release notes
The outdated winpty.pyi issue is resolved, so the package's type stub is no longer outdated.
3.0.3release notes

Closing a PTY no longer waits a fixed five seconds; a blocking read after child exit returns in about 175 ms, and teardown no longer cancels I/O owned by the host application.
3.1.2release notes
Spawning an executable whose path contains a space now works across both backends, with argv[0] intact.
3.1.2release notes
Large output is no longer truncated after the child exits; output drains in full and reaches EOF.
3.1.1release notes
Closing a PTY no longer hangs or leaves the child process orphaned due to a teardown deadlock against ConPTY 1.25.
3.1.1release notes
Arguments passed to the WinPTY backend are no longer lost.
3.1.1release notes
The published wheels now include the required native binaries, making the x64 and arm64 releases usable.
3.0.5release notes
Event-driven teardown fixes data loss when a child exits quickly and removes the Drop CPU-spin.
3.0.4release notes

C++ dependencies were dropped as the PTY implementation moved to winpty-rs, simplifying dependencies and the building environment.
2.0.0release notes
PTY no longer accepts the encoding keyword argument.
2.0.0release notes
PtyProcess no longer accepts the encoding keyword argument.
2.0.0release notes

The reading thread is now blocking and no longer consumes CPU unnecessarily.
2.0.0release notes