Python 3.13.9 released
Python 3.13.9 is a maintenance update that addresses a significant regression issue that Python 3.13.8 introduced. This quick release fixes a bug that caused the inspect.getsourcelines function to fail when it found a decorator followed by a comment or an empty line. This bug was reported as issue gh-139783.
This update solely addresses the previously mentioned regression. All other features and functions are the same as they were in Python 3.13.8.
Users are directed to the latest release series, Python 3.14.x, which is a big deal because it is the first new feature release series for Python 3. People who want to get the newest version can do so by clicking on the link.
There are a lot of cool new features and improvements in the 3.13 series compared to the 3.12 series that came before it.
The addition of a new interactive interpreter based on PyPy's is one of the most important changes. This new interface has more features, like the ability to edit multiple lines at once, support for colors to make things look better, and even colorized exception tracebacks, which make it an essential tool for developers.
Python 3.13 also has experimental features that are meant to push the limits of concurrent execution. The free-threaded build mode turns off the Global Interpreter Lock, which lets more threads run at the same time. However, this is still an experimental feature that only works with Windows and macOS installers.
Also, a basic Just-In-Time (JIT) compiler is added as a starting point for future performance improvements. This new feature aims to improve Python's performance by running some parts of the code directly in machine code.
The locals() built-in function in Python 3.13 also gets better semantics. This update makes debuggers work more reliably and consistently when used with returned mappings.
Other important changes include the addition of a modified version of mimalloc, which is an optional memory allocator that is turned on by default and is needed for the free-threaded build mode. Also, removing the leading indentation from docstrings improves them, which saves memory and makes .pyc files smaller.
The dbm module has also been improved with a new SQLite-based backend that is used by default when making new files. From now on, Python 3.13 will only work with macOS versions 10.13 (High Sierra) or later. It will no longer work with older versions of macOS.
Along with these improvements, there have been several important changes made to platform support and tier classification. In particular:
- WASI has been elevated from Tier 1 to Tier 2 supported status.
- Emscripten is no longer officially supported but remains accessible through Pyodide.
- iOS and Android are now classified as Tier 3 supported platforms.
Finally, Python 3.13 makes a number of improvements to typing. With type defaults in type parameters, developers have more freedom when working with generics. Also, new type narrowing annotations have been added to make type checking more accurate and faster.
Python Insider: Python 3.13.9 is now available!
