README.rst

This is Python version 3.7.0 alpha 1

Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011,2012, 2013, 2014, 2015, 2016, 2017 Python Software Foundation. All rightsreserved.

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

General Information

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

Contributing to CPython

For more complete instructions on contributing to CPython development,see theDeveloper Guide.

Using Python

Installable Python kits, and information about using Python, are available atpython.org.

Build Instructions

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

./configuremakemake testsudo make install

This will install Python as python3.

You can pass many options to the configure script; run./configure --helpto find out more. On macOS and Cygwin, the executable is calledpython.exe;elsewhere it's justpython.

On macOS, if you have configured Python with--enable-framework, youshould usemake frameworkinstall to do the installation. Note that thisinstalls the Python executable in a place that is not normally on your PATH,you may want to set up a symlink in/usr/local/bin.

On Windows, seePCbuild/readme.txt.

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

mkdir debugcd debug../configure --with-pydebugmakemake test

(This will fail if youalso built at the top-level directory. You should doamake clean at the toplevel first.)

To get an optimized build of Python,configure --enable-optimizationsbefore you runmake. This sets the default make targets up to enableProfile Guided Optimization (PGO) and may be used to auto-enable Link TimeOptimization (LTO) on some platforms. For more details, see the sectionsbelow.

Profile Guided Optimization

PGO takes advantage of recent versions of the GCC or Clang compilers. If ran,make profile-opt will do several steps.

First, the entire Python directory is cleaned of temporary files that may haveresulted in a previous compilation.

Then, an instrumented version of the interpreter is built, using suitablecompiler flags for each flavour. Note that this is just an intermediary stepand the binary resulted after this step is not good for real life workloads, asit has profiling instructions embedded inside.

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

Finally, the last step is to rebuild the interpreter, using the informationcollected in the previous one. The end result will be a Python binary that isoptimized and suitable for distribution or production installation.

Link Time Optimization

Enabled via configure's--with-lto flag. LTO takes advantage of theability of recent compiler toolchains to optimize across the otherwisearbitrary.o file boundary when building final executables or sharedlibraries for additional performance gains.

What's New

We have a comprehensive overview of the changes in theWhat's New in Python3.7 document. For a moredetailed change log, readMisc/NEWS, but a fullaccounting of changes can only be gleaned from thecommit history.

If you want to install multiple versions of Python see the section belowentitled "Installing multiple versions".

Documentation

Documentation for Python 3.7 is online,updated daily.

It can also be downloaded in many formats for faster access. The documentationis downloadable in HTML, PDF, and reStructuredText formats; the latter versionis primarily for documentation authors, translators, and people with specialformatting requirements.

For information about building Python's documentation, refer toDoc/README.rst.

Converting From Python 2.x to 3.x

Significant backward incompatible changes were made for the release of Python3.0, which may cause programs written for Python 2 to fail when run with Python3. For more information about porting your code from Python 2 to Python 3, seethePorting HOWTO.

Testing

To test the interpreter, typemake test in the top-level directory. Thetest set produces some output. You can generally ignore the messages aboutskipped tests due to optional features which can't be imported. If a messageis 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 andmemory. To enable these tests, runmake testall.

If any tests fail, you can re-run the failing test(s) in verbose mode:

make test TESTOPTS="-v test_that_failed"

If the failure persists and appears to be a problem with Python rather thanyour environment, you canfile a bug report andinclude relevant output from that command to show the issue.

Installing multiple versions

On Unix and Mac systems if you intend to install multiple versions of Pythonusing the same installation prefix (--prefix argument to the configurescript) you must take care that your primary python executable is notoverwritten by the installation of a different version. All files anddirectories installed usingmake altinstall contain the major and minorversion and can thus live side-by-side.make install also creates${prefix}/bin/python3 which refers to${prefix}/bin/pythonX.Y. If youintend to install multiple versions using the same prefix you must decide whichversion (if any) is your "primary" version. Install that version usingmakeinstall. Install all other versions usingmake altinstall.

For example, if you want to install Python 2.7, 3.6, and 3.7 with 3.7 being theprimary version, you would executemake install in your 3.7 build directoryandmake altinstall in the others.

Issue Tracker and Mailing List

Bug reports are welcome! You can use theissue tracker to report bugs, and/or submit pull requestsonGitHub.

You can also follow development discussion on thepython-dev mailing list.

Proposals for enhancement

If you have a proposal to change Python, you may want to send an email to thecomp.lang.python orpython-ideas mailing lists for initial feedback. APython Enhancement Proposal (PEP) may be submitted if your idea gains ground.All current PEPs, as well as guidelines for submitting a new PEP, are listed atpython.org/dev/peps/.

Release Schedule

SeePEP 537 for Python 3.7 release details.

Copyright and License Information

Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011,2012, 2013, 2014, 2015, 2016 Python Software Foundation. All rights reserved.

Copyright (c) 2000 BeOpen.com. All rights reserved.

Copyright (c) 1995-2001 Corporation for National Research Initiatives. Allrights reserved.

Copyright (c) 1991-1995 Stichting Mathematisch Centrum. All rights reserved.

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

This Python distribution containsno GNU General Public License (GPL) code,so it may be used in proprietary projects. There are interfaces to some GNUcode but these are entirely optional.

All trademarks referenced herein are property of their respective holders.