python/cpython

This is Python version 3.16.0 alpha 1+dev =========================================

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Copyright © 2001 Python Software Foundation. All rights reserved.

See the end of this file for further copyright and license information.

.. contents::

General Information -------------------

• Website: https://www.python.org
• Source code: https://github.com/python/cpython
• Issue tracker: https://github.com/python/cpython/issues
• Documentation: https://docs.python.org
• Developer's Guide: https://devguide.python.org/

For more complete instructions on contributing to CPython development, see the Developer Guide_.

.. _Developer Guide: https://devguide.python.org/

Using Python ------------

Installable Python kits, and information about using Python, are available at python.org_.

.. _python.org: https://www.python.org/

Build Instructions ------------------

On Unix, Linux, BSD, macOS, and Cygwin::

./configure make make test sudo make install

This will install Python as `python3`.

You can pass many options to the configure script; run `./configure --help` to find out more. On macOS case-insensitive file systems and on Cygwin, the executable is called `python.exe; elsewhere it's just python`.

Building a complete Python installation requires the use of various additional third-party libraries, depending on your build platform and configure options. Not all standard library modules are buildable or usable on all platforms. Refer to the Install dependencies _ section of the Developer Guide_ for current detailed information on dependencies for various Linux distributions and macOS.

On macOS, there are additional configure and build options related to macOS framework and universal builds. Refer to `Mac/README.rst `_.

On Windows, see `PCbuild/readme.txt `_.

To build Windows packages, see `PC/layout/README.md `_.

If you wish, you can create a subdirectory and invoke configure from there. For example::

mkdir debug cd debug ../configure --with-pydebug make make test

(This will fail if you also built at the top-level directory. You should do a `make clean` at the top-level first.)

To get an optimized build of Python, run `configure --enable-optimizations` before you run `make`. This sets the default make targets up to enable Profile Guided Optimization (PGO) and may be used to auto-enable Link Time Optimization (LTO) on some platforms. For more details, see the sections below.

Profile Guided Optimization ^^^^^^^^^^^^^^^^^^^^^^^^^^^

PGO takes advantage of recent versions of the GCC or Clang compilers. If used, either via `configure --enable-optimizations` or by manually running `make profile-opt` regardless of configure flags, the optimized build process will perform the following steps:

The entire Python directory is cleaned of temporary files that may have resulted from a previous compilation.

An instrumented version of the interpreter is built, using suitable compiler flags for each flavor. Note that this is just an intermediary step. The binary resulting from this step is not good for real-life workloads as it has profiling instructions embedded inside.

After the instrumented interpreter is built, the Makefile will run a training workload. This is necessary in order to profile the interpreter's execution. Note also that any output, both stdout and stderr, that may appear at this step is suppressed.

The final step is to build the actual interpreter, using the information collected from the instrumented one. The end result will be a Python binary that is optimized; suitable for distribution or production installation.

Link Time Optimization ^^^^^^^^^^^^^^^^^^^^^^

Enabled via configure's `--with-lto` flag. LTO takes advantage of the ability of recent compiler toolchains to optimize across the otherwise arbitrary `.o` file boundary when building final executables or shared libraries for additional performance gains.

What's New ----------

We have a comprehensive overview of the changes in the `What's new in Python 3.16 `_ document. For a more detailed change log, read `Misc/NEWS `_, but a full accounting of changes can only be gleaned from the `commit history `_.

If you want to install multiple versions of Python, see the section below entitled "Installing multiple versions".

Documentation -------------

Documentation for Python 3.16 _ is online, updated daily.

It can also be downloaded in many formats for faster access. The documentation is downloadable in HTML, EPUB, and reStructuredText formats; the latter version is primarily for documentation authors, translators, and people with special formatting requirements.

For information about building Python's documentation, refer to `Doc/README.rst `_.

Testing -------

To test the interpreter, type `make test` in the top-level directory. The test set produces some output. You can generally ignore the messages about skipped tests due to optional features which can't be imported. If a message is printed about a failed test or a traceback or core dump is produced, something is wrong.

By default, tests are prevented from overusing resources like disk space and memory. To enable these tests, run `make buildbottest`.

If any tests fail, you can re-run the failing test(s) in verbose mode. For example, if `test_os and test_gdb` failed, you can run::

make test TESTOPTS="-v test_os test_gdb"

If the failure persists and appears to be a problem with Python rather than your environment, you can `file a bug report `_ and include relevant output from that command to show the issue.

See Running & Writing Tests _ for more on running tests.

Installing multiple versions ----------------------------

On Unix and Mac systems if you intend to install multiple versions of Python using the same installation prefix (`--prefix` argument to the configure script) you must take care that your primary python executable is not overwritten by the installation of a different version. All files and directories installed using `make altinstall` contain the major and minor version and can thus live side-by-side. `make install` also creates `${prefix}/bin/python3 which refers to ${prefix}/bin/python3.X`. If you intend to install multiple versions using the same prefix you must decide which version (if any) is your "primary" version. Install that version using `make install. Install all other versions using make altinstall`.

For example, if you want to install Python 2.7, 3.6, and 3.15 with 3.15 being the primary version, you would execute `make install` in your 3.15 build directory and `make altinstall` in the others.

Release Schedule ----------------

See PEP 826 __ for Python 3.16 release details.

Copyright and License Information ---------------------------------

Copyright © 2001 Python Software Foundation. All rights reserved.

Copyright © 2000 BeOpen.com. All rights reserved.

Copyright © 1995-2001 Corporation for National Research Initiatives. All rights reserved.

Copyright © 1991-1995 Stichting Mathematisch Centrum. All rights reserved.

See the LICENSE _ for information on the history of this software, terms & conditions for usage, and a DISCLAIMER OF ALL WARRANTIES.

This Python distribution contains no GNU General Public License (GPL) code, so it may be used in proprietary projects. There are interfaces to some GNU code but these are entirely optional.

All trademarks referenced herein are property of their respective holders.