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title: Python 3.15.0 candidate 3 is here! | daily.dev
description: Python 3.15.0 release candidate 3 has arrived unexpectedly, delaying the planned final release by a week to accommodate last-minute lazy-import bug fixes. This...
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# Python 3.15.0 candidate 3 is here!

**[Python Insider](https://daily.dev/sources/python)** · 5 min read · 0 upvotes · 0 comments

## Summary

Python 3.15.0 release candidate 3 has arrived unexpectedly, delaying the planned final release by a week to accommodate last-minute lazy-import bug fixes. This is the final planned release candidate before 3.15.0 ships on 2026-10-09, with no further ABI changes expected. Maintainers are urged to publish 3.15-compatible wheels on PyPI. Notable new features include PEP 810 explicit lazy imports, a frozendict builtin, unpacking in comprehensions, UTF-8 as default encoding, and a JIT compiler upgrade delivering 7-12% performance gains. Separately, a macOS 27.0 operating system change is causing tkinter-based GUI apps like IDLE to hang when opening dialogs, a known issue tracked on the CPython bug tracker.

## Full article

daily.dev links to this article rather than hosting it. Read it at the original source: <https://blog.python.org/2026/10/python-3150-rc3>

## Questions this post answers

### When is Python 3.15.0 final scheduled to be released?

Python 3.15.0 final is scheduled for October 9, 2026, after an extra release candidate (3.15.0rc3) was issued to include last-minute lazy-import bug fixes. The rc3 build contains around 156 bugfixes, build improvements, and documentation changes from 82 contributors since rc2, and no further ABI changes are expected before final.

_Teams planning upgrades can track python version milestones like this on daily.dev._

### Why does IDLE hang when opening the About or Settings dialog on macOS 27.0?

An operating system behavior change in macOS 27.0 affects the Tk graphics toolkit, causing tkinter-based GUI applications such as IDLE to hang with a spinning beach ball when menu commands open dialogs like About IDLE, Settings, or Open Module. This is believed to impact all current Tk versions and thus all current Python versions; a workaround is tracked under CPython issue #158053, and deferring the macOS upgrade is recommended until a fix lands.

_Developers debugging platform-specific GUI breakage can follow issues like this via daily.dev._

### What major new features are in Python 3.15 compared to 3.14?

Python 3.15 adds PEP 810 explicit lazy imports for faster startup, a frozendict builtin (PEP 814), a sentinel builtin (PEP 661), unpacking in comprehensions (PEP 798), UTF-8 as the default encoding (PEP 686), and package startup configuration files (PEP 829). The experimental JIT compiler also gained 7-8% performance improvement on x86-64 Linux and 11-12% on AArch64 macOS over prior interpreters.

_Planning a Python upgrade? Track new language features and PEPs like these on daily.dev._

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---

Tags: [#python](https://daily.dev/tags/python), [#cpython](https://daily.dev/tags/cpython)

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