🌐 Mailman 3 July 2025 - Python-list - python.org

Searching for a file
by Rob Cliffe Aug. 9, 2025

Aug. 9, 2025

It occurs to me that it might be useful if Python provided a function to search for a file with a given name in various directories (much as the import.import_lib function searches for a module in the directories in sys.path). This function would perhaps be best placed in the os.path or os modules. To start the ball rolling, I offer this version: import sys import os def findfile(fileName, *PathLists): if not PathLists: # Default to searching just sys.path: PathLists = [ sys.path ] # This may or may not be the most useful default; # there is a case for having no default, forcing calls of this function # to explicitly specifiy which paths they want to search, # and perhaps raise an Exception if they don't; # suggestions welcome. for pList in PathLists: # if pList is a str, assume it is a semicolon-separated list of directories # (like the PATH and PYTHONPATH environment variables); # otherwise assume it is a sequence of paths (like sys.path): if isinstance(pList, str): pList = pList.split(';') for path in pList: filePath = os.path.join(path, fileName) if os.path.isfile(filePath): return filePath # Return first match found. # Another possibility is to return a list of all matches. return None Then e.g. print(findfile('os.py')) would print something like C:\Python311\Lib\os.py This idea was partly inspired by Michael Stemper asking about best practice for placing, and finding, a configuration file. Thoughts? Best wishes Rob Cliffe

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Python 3.14 release candidate 1 is go!
by Hugo van Kemenade July 22, 2025

July 22, 2025

It’s the first 3.14 release candidate! https://www.python.org/downloads/release/python-3140rc1/ This release, 3.14.0rc1, is the penultimate release preview. Entering the release candidate phase, only reviewed code changes which are clear bug fixes are allowed between this release candidate and the final release. The second candidate (and the last planned release preview) is scheduled for Tuesday, 2025-08-26, while the official release of 3.14.0 is scheduled for Tuesday, 2025-10-07. There will be no ABI changes from this point forward in the 3.14 series, and the goal is that there will be as few code changes as possible. Call to action We strongly encourage maintainers of third-party Python projects to prepare their projects for 3.14 during this phase, and where necessary publish Python 3.14 wheels on PyPI to be ready for the final release of 3.14.0, and to help other projects do their own testing. Any binary wheels built against Python 3.14.0rc1 will work with future versions of Python 3.14. As always, report any issues to the Python bug tracker. Please keep in mind that this is a preview release and while it’s as close to the final release as we can get it, its use is not recommended for production environments. Core developers: time to work on documentation now - Are all your changes properly documented? - Are they mentioned in What’s New? - Did you notice other changes you know of to have insufficient documentation? Major new features of the 3.14 series, compared to 3.13 Some of the major new features and changes in Python 3.14 are: New features - PEP 779: Free-threaded Python is officially supported - PEP 649: The evaluation of type annotations is now deferred, improving the semantics of using annotations. - PEP 750: Template string literals (t-strings) for custom string processing, using the familiar syntax of f-strings. - PEP 734: Multiple interpreters in the stdlib. - PEP 784: A new module compression.zstd providing support for the Zstandard compression algorithm. - PEP 758: except and except* expressions may now omit the brackets. - Syntax highlighting in PyREPL, and support for color in unittest, argparse, json and calendar CLIs. - PEP 768: A zero-overhead external debugger interface for CPython. - UUID versions 6-8 are now supported by the uuid module, and generation of versions 3-5 are up to 40% faster. - PEP 765: Disallow return/break/continue that exit a finally block. - PEP 741: An improved C API for configuring Python. - A new type of interpreter. For certain newer compilers, this interpreter provides significantly better performance. Opt-in for now, requires building from source. - Improved error messages. - Builtin implementation of HMAC with formally verified code from the HACL* project. - A new command-line interface to inspect running Python processes using asynchronous tasks. - The pdb module now supports remote attaching to a running Python process. (Hey, fellow core developer, if a feature you find important is missing from this list, let Hugo know.) For more details on the changes to Python 3.14, see What’s new in Python 3.14. The next pre-release of Python 3.14 will be the final release candidate, 3.14.0rc2, scheduled for 2025-08-26. https://docs.python.org/3.14/whatsnew/3.14.html Build changes - PEP 761: Python 3.14 and onwards no longer provides PGP signatures for release artifacts. Instead, Sigstore is recommended for verifiers. - Official macOS and Windows release binaries include an experimental JIT compiler. Incompatible changes, removals and new deprecations - Incompatible changes - Python removals and deprecations - C API removals and deprecations - Overview of all pending deprecations Python install manager The installer we offer for Windows is being replaced by our new install manager, which can be installed from the Windows Store or from its download page. See our documentation for more information. The JSON file available for download below contains the list of all the installable packages available as part of this release, including file URLs and hashes, but is not required to install the latest release. The traditional installer will remain available throughout the 3.14 and 3.15 releases. More resources - Online documentation https://docs.python.org/3.14/ - PEP 745: 3.14 Release Schedule https://peps.python.org/pep-0745/ - Report bugs at https://github.com/python/cpython/issues - Help fund Python and its community: https://www.python.org/psf/donations/ And now for something completely different Today, 22nd July, is Pi Approximation Day, because 22/7 is a common approximation of π and closer to π than 3.14. 22/7 is a Diophantine approximation, named after Diophantus of Alexandria (3rd century CE), which is a way of estimating a real number as a ratio of two integers. 22/7 has been known since antiquity; Archimedes (3rd century BCE) wrote the first known proof that 22/7 overestimates π by comparing 96-sided polygons to the circle it circumscribes. Another approximation is 355/113. In Chinese mathematics, 22/7 and 355/113 are respectively known as Yuelü (约率; yuēlǜ; “approximate ratio”) and Milü (密率; mìlǜ; “close ratio”). Happy Pi Approximation Day! Enjoy the new release Thanks to all of the many volunteers who help make Python Development and these releases possible! Please consider supporting our efforts by volunteering yourself or through organisation contributions to the Python Software Foundation. Regards from a Helsinki heatwave after an excellent EuroPython, Your release team, Hugo van Kemenade Ned Deily Steve Dower Łukasz Langa

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Announcement: distlib 0.4.0 released on PyPI
by Vinay Sajip July 17, 2025

July 17, 2025

Version 0.4.0 of distlib has recently been released on PyPI [1]. For newcomers, distlib is a library of packaging functionality which is intended to be usable as the basis for third-party packaging tools. The main changes in this release are as follows: * Add the ``interpret_parsed`` function to ``markers``. * Fix #238: Add build tag to wheel metadata if specified. * Fix #243: Update to support free-threading version of Python (3.13t). * Fix #246: Support subdirectories in the dist-info directory. Thanks to Pieter P for the patch. * Fix #248: Fix path normalization issue caused by the fix for #246. * Move import in script wrapper to ``if __name__ == 'main'`` clause. * Fix #245: Skip test_package_data if a ``SKIP_EXT_PACKAGE_DATA`` environment variable is present. A more detailed change log is available at [2]. Please try it out, and if you find any problems or have any suggestions for improvements, please give some feedback using the issue tracker at [3]. Regards, Vinay Sajip [1] https://pypi.org/project/distlib/0.4.0/ [2] https://distlib.readthedocs.io/en/latest/overview.html#change-log-for-distl… [3] https://github.com/pypa/distlib/issues/new/choose

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Python 3.14.0 beta 4 is here!
by Hugo van Kemenade July 8, 2025

July 8, 2025

It’s the final 3.14 beta! https://www.python.org/downloads/release/python-3140b4/ This is a beta preview of Python 3.14 Python 3.14 is still in development. This release, 3.14.0b4, is the last of four planned beta releases. Beta release previews are intended to give the wider community the opportunity to test new features and bug fixes and to prepare their projects to support the new feature release. We strongly encourage maintainers of third-party Python projects to test with 3.14 during the beta phase and report issues found to the Python bug tracker as soon as possible. While the release is planned to be feature-complete entering the beta phase, it is possible that features may be modified or, in rare cases, deleted up until the start of the release candidate phase (Tuesday 2025-07-22). Our goal is to have no ABI changes after beta 4 and as few code changes as possible after the first release candidate. To achieve that, it will be extremely important to get as much exposure for 3.14 as possible during the beta phase. This includes creating pre-release wheels for 3.14, as it helps other projects to do their own testing. However, we recommend that your regular production releases wait until 3.14.0rc1, to avoid the risk of ABI breaks. Please keep in mind that this is a preview release and its use is not recommended for production environments. Major new features of the 3.14 series, compared to 3.13 Some of the major new features and changes in Python 3.14 are: New features - PEP 779: Free-threaded Python is officially supported - PEP 649: The evaluation of type annotations is now deferred, improving the semantics of using annotations. - PEP 750: Template string literals (t-strings) for custom string processing, using the familiar syntax of f-strings. - PEP 734: Multiple interpreters in the stdlib. - PEP 784: A new module compression.zstd providing support for the Zstandard compression algorithm. - PEP 758: except and except* expressions may now omit the brackets. - Syntax highlighting in PyREPL, and support for color in unittest, argparse, json and calendar CLIs. - PEP 768: A zero-overhead external debugger interface for CPython. - UUID versions 6-8 are now supported by the uuid module, and generation of versions 3-5 and 8 are up to 40% faster. - PEP 765: Disallow return/break/continue that exit a finally block. - PEP 741: An improved C API for configuring Python. - A new type of interpreter. For certain newer compilers, this interpreter provides significantly better performance. Opt-in for now, requires building from source. - Improved error messages. - Builtin implementation of HMAC with formally verified code from the HACL* project. - A new command-line interface to inspect running Python processes using asynchronous tasks. - The pdb module now supports remote attaching to a running Python process. (Hey, fellow core developer, if a feature you find important is missing from this list, let Hugo know.) For more details on the changes to Python 3.14, see What’s new in Python 3.14. The next pre-release of Python 3.14 will be the first release candidate, 3.14.0rc1, scheduled for 2025-07-22. https://docs.python.org/3.14/whatsnew/3.14.html Build changes - PEP 761: Python 3.14 and onwards no longer provides PGP signatures for release artifacts. Instead, Sigstore is recommended for verifiers. - Official macOS and Windows release binaries include an experimental JIT compiler. Incompatible changes, removals and new deprecations - Incompatible changes - Python removals and deprecations - C API removals and deprecations - Overview of all pending deprecations Python install manager The installer we offer for Windows is being replaced by our new install manager, which can be installed from the Windows Store or from its download page. See our documentation for more information. The JSON file available for download below contains the list of all the installable packages available as part of this release, including file URLs and hashes, but is not required to install the latest release. The traditional installer will remain available throughout the 3.14 and 3.15 releases. More resources - Online documentation](https://docs.python.org/3.14/) - PEP 745](https://peps.python.org/pep-0745/), 3.14 Release Schedule - Report bugs at https://github.com/python/cpython/issues - Help fund Python and its community: https://www.python.org/psf/donations/ And now for something completely different All this talk of π and yet some say π is wrong. Tau Day (June 28th, 6/28 in the US) celebrates τ as the “true circle constant”, as the ratio of a circle’s circumference to its radius, C/r = 6.283185… The Tau Manifesto declares π “a confusing and unnatural choice for the circle constant”, in part because “2π occurs with astonishing frequency throughout mathematics”. If you wish to embrace τ the good news is PEP 628 added math.tau to Python 3.6 in 2016: When working with radians, it is trivial to convert any given fraction of a circle to a value in radians in terms of tau. A quarter circle is tau/4, a half circle is tau/2, seven 25ths is 7*tau/25, etc. In contrast with the equivalent expressions in terms of pi (pi/2, pi, 14*pi/25), the unnecessary and needlessly confusing multiplication by two is gone. Enjoy the new release Thanks to all of the many volunteers who help make Python Development and these releases possible! Please consider supporting our efforts by volunteering yourself or through organisation contributions to the Python Software Foundation. Regards from a cloudy Helsinki, looking forward to Prague and EuroPython next week, Your release team, Hugo van Kemenade Ned Deily Steve Dower Łukasz Langa

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configparser get non-existent boolean
by Rob Cliffe July 1, 2025

July 1, 2025

I was surprised to find that in configparser, getboolean() does not raise KeyError for a non-existent config parameter. Demo program (Python 3.11.5, Windows 11): import configparser config = configparser.ConfigParser() config.read('ThisFileDoesNotExist.ini') # This line could be removed MY_BOOL= config['DEFAULT'].getboolean('MY_BOOL') # This does NOT raise an Exception! print(f"{MY_BOOL=}") MY_STR = config['DEFAULT']['MY_STR'] # This does raise an Exception, naturally The output: MY_BOOL=None Traceback (most recent call last): File "R:\Test.py", line 7, in <module> MY_STR = config['DEFAULT']['MY_STR'] # This does raise an Exception, naturally ~~~~~~~~~~~~~~~~~^^^^^^^^^^ File "C:\Python313\Lib\configparser.py", line 1276, in __getitem__ raise KeyError(key) KeyError: 'MY_STR' Is there a good reason for this? Best wishes, Rob Cliffe

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Assignment of global variables in a script.
by Popov, Dmitry Yu July 1, 2025

July 1, 2025

Dear Sirs. I found the following sentence in the Python documentation: "The statements executed by the top-level invocation of the interpreter, either read from a script file or interactively, are considered part of a module called __main__<https://docs.python.org/3.11/library/__main__.html#module-__main__>, so they have their own global namespace." In other words, global assignments of variables placed directly in a module's name space are also "statements executed by the top-level invocation of the interpreter", if the module is executed as a script. Is it stable at all to assign global variables directly in a module which runs as a script? Speaking practically, I have not observed any problem so far. Regards, Dmitry Popov

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