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This is Python version 3.0.1

For notes specific to this release, see RELNOTES in this directory. Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Python Software Foundation. All rights reserved.

Python 3 (a.k.a. "Python 3000" or "Py3k", and released as Python 3.0) is a new version of the language, which is incompatible with the 2.x line of releases. The language is mostly the same, but many details, especially how built-in objects like dictionaries and strings work, have changed considerably, and a lot of deprecated features have finally been removed.


Documentation for Python 3.0 is online, updated twice a day:

All documentation is also available online at the Python web site (, see below). It is available online for occasional reference, and it can be downloaded in many formats for faster local access. The documentation is downloadable in HTML, PostScript, PDF, LaTeX (through 2.5), and reStructuredText (2.6, 3.0, and going forward) formats; the LaTeX and reStructuredText versions are primarily for documentation authors, translators, and people with special formatting requirements.

This is a work in progress; please help improve it!

The design documents for Python 3 are also online. While the reference documentation is being updated, the PEPs are often the best source of information about new features. Start by reading PEP 3000:

What's New

For an overview of what's new in Python 3.0, see Guido van Rossum's blog at

We try to eventually have a comprehensive overview of the changes in the "What's New in Python 3.0" document, found at

Please help improve it!

For a more detailed change log, read Misc/NEWS, though this file, too, is incomplete, and also doesn't list anything merged in from the 2.6 release.

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

Proposals for enhancement

If you have a proposal to change Python, you may want to send an email to the comp.lang.python or python-ideas mailing lists for initial feedback. A Python 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 at

Converting From Python 2.x to 3.0

Python 2.6 contains features to help locating and updating code that needs to be changed when migrating to Python 3.

A source-to-source translation tool, "2to3", can take care of the mundane task of converting large amounts of source code. It is not a complete solution but is complemented by the deprecation warnings in 2.6. This tool is currently available via the Subversion sandbox:

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/python which refers to ${prefix}/bin/pythonX.Y. 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 2.5, 2.6 and 3.0 with 2.6 being the primary version, you would execute "make install" in your 2.6 build directory and "make altinstall" in the others.

Issue Tracker and Mailing List

We're soliciting bug reports about all aspects of the language. Fixes are also welcome, preferable in unified diff format. Please use the issue tracker:

If you're not sure whether you're dealing with a bug or a feature, use the mailing list:

To subscribe to the list, use the Mailman form:

Build Instructions

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

./configure make make test sudo make install # or "make altinstall"

You can pass many options to the configure script; run "./configure --help" to find out more. On OSX and Cygwin, the executable is called python.exe; elsewhere it's just python.

On Mac OS X, if you have configured Python with --enable-framework, you should use "make frameworkinstall" to do the installation. Note that this installs 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, see PCbuild/readme.txt.

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 toplevel first.)