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==================
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General Python FAQ
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==================
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.. only:: html
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.. contents::
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General Information
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===================
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What is Python?
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---------------
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Python is an interpreted, interactive, object-oriented programming language. It
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incorporates modules, exceptions, dynamic typing, very high level dynamic data
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types, and classes. It supports multiple programming paradigms beyond
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object-oriented programming, such as procedural and functional programming.
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Python combines remarkable power with very clear syntax. It has interfaces to
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many system calls and libraries, as well as to various window systems, and is
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extensible in C or C++. It is also usable as an extension language for
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applications that need a programmable interface. Finally, Python is portable:
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it runs on many Unix variants including Linux and macOS, and on Windows.
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To find out more, start with :ref:`tutorial-index`. The `Beginner's Guide to
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Python <https://wiki.python.org/moin/BeginnersGuide>`_ links to other
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introductory tutorials and resources for learning Python.
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What is the Python Software Foundation?
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---------------------------------------
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The Python Software Foundation is an independent non-profit organization that
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holds the copyright on Python versions 2.1 and newer. The PSF's mission is to
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advance open source technology related to the Python programming language and to
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publicize the use of Python. The PSF's home page is at
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https://www.python.org/psf/.
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Donations to the PSF are tax-exempt in the US. If you use Python and find it
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helpful, please contribute via `the PSF donation page
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<https://www.python.org/psf/donations/>`_.
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Are there copyright restrictions on the use of Python?
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------------------------------------------------------
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You can do anything you want with the source, as long as you leave the
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copyrights in and display those copyrights in any documentation about Python
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that you produce. If you honor the copyright rules, it's OK to use Python for
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commercial use, to sell copies of Python in source or binary form (modified or
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unmodified), or to sell products that incorporate Python in some form. We would
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still like to know about all commercial use of Python, of course.
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See `the PSF license page <https://www.python.org/psf/license/>`_ to find further
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explanations and a link to the full text of the license.
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The Python logo is trademarked, and in certain cases permission is required to
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use it. Consult `the Trademark Usage Policy
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<https://www.python.org/psf/trademarks/>`__ for more information.
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Why was Python created in the first place?
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------------------------------------------
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Here's a *very* brief summary of what started it all, written by Guido van
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Rossum:
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I had extensive experience with implementing an interpreted language in the
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ABC group at CWI, and from working with this group I had learned a lot about
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language design. This is the origin of many Python features, including the
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use of indentation for statement grouping and the inclusion of
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very-high-level data types (although the details are all different in
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Python).
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I had a number of gripes about the ABC language, but also liked many of its
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features. It was impossible to extend the ABC language (or its
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implementation) to remedy my complaints -- in fact its lack of extensibility
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was one of its biggest problems. I had some experience with using Modula-2+
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and talked with the designers of Modula-3 and read the Modula-3 report.
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Modula-3 is the origin of the syntax and semantics used for exceptions, and
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some other Python features.
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I was working in the Amoeba distributed operating system group at CWI. We
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needed a better way to do system administration than by writing either C
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programs or Bourne shell scripts, since Amoeba had its own system call
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interface which wasn't easily accessible from the Bourne shell. My
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experience with error handling in Amoeba made me acutely aware of the
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importance of exceptions as a programming language feature.
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It occurred to me that a scripting language with a syntax like ABC but with
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access to the Amoeba system calls would fill the need. I realized that it
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would be foolish to write an Amoeba-specific language, so I decided that I
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needed a language that was generally extensible.
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During the 1989 Christmas holidays, I had a lot of time on my hand, so I
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decided to give it a try. During the next year, while still mostly working
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on it in my own time, Python was used in the Amoeba project with increasing
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success, and the feedback from colleagues made me add many early
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improvements.
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In February 1991, after just over a year of development, I decided to post to
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USENET. The rest is in the ``Misc/HISTORY`` file.
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What is Python good for?
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------------------------
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Python is a high-level general-purpose programming language that can be applied
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to many different classes of problems.
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The language comes with a large standard library that covers areas such as
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string processing (regular expressions, Unicode, calculating differences between
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files), Internet protocols (HTTP, FTP, SMTP, XML-RPC, POP, IMAP, CGI
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programming), software engineering (unit testing, logging, profiling, parsing
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Python code), and operating system interfaces (system calls, filesystems, TCP/IP
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sockets). Look at the table of contents for :ref:`library-index` to get an idea
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of what's available. A wide variety of third-party extensions are also
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available. Consult `the Python Package Index <https://pypi.org>`_ to
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find packages of interest to you.
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How does the Python version numbering scheme work?
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--------------------------------------------------
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Python versions are numbered A.B.C or A.B. A is the major version number -- it
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is only incremented for really major changes in the language. B is the minor
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version number, incremented for less earth-shattering changes. C is the
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micro-level -- it is incremented for each bugfix release. See :pep:`6` for more
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information about bugfix releases.
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Not all releases are bugfix releases. In the run-up to a new major release, a
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series of development releases are made, denoted as alpha, beta, or release
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candidate. Alphas are early releases in which interfaces aren't yet finalized;
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it's not unexpected to see an interface change between two alpha releases.
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Betas are more stable, preserving existing interfaces but possibly adding new
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modules, and release candidates are frozen, making no changes except as needed
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to fix critical bugs.
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Alpha, beta and release candidate versions have an additional suffix. The
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suffix for an alpha version is "aN" for some small number N, the suffix for a
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beta version is "bN" for some small number N, and the suffix for a release
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candidate version is "cN" for some small number N. In other words, all versions
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labeled 2.0aN precede the versions labeled 2.0bN, which precede versions labeled
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2.0cN, and *those* precede 2.0.
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You may also find version numbers with a "+" suffix, e.g. "2.2+". These are
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unreleased versions, built directly from the CPython development repository. In
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practice, after a final minor release is made, the version is incremented to the
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next minor version, which becomes the "a0" version, e.g. "2.4a0".
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See also the documentation for :data:`sys.version`, :data:`sys.hexversion`, and
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:data:`sys.version_info`.
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How do I obtain a copy of the Python source?
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--------------------------------------------
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The latest Python source distribution is always available from python.org, at
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https://www.python.org/downloads/. The latest development sources can be obtained
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at https://github.com/python/cpython/.
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The source distribution is a gzipped tar file containing the complete C source,
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Sphinx-formatted documentation, Python library modules, example programs, and
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several useful pieces of freely distributable software. The source will compile
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and run out of the box on most UNIX platforms.
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Consult the `Getting Started section of the Python Developer's Guide
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<https://devguide.python.org/setup/>`__ for more
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information on getting the source code and compiling it.
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How do I get documentation on Python?
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-------------------------------------
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.. XXX mention py3k
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The standard documentation for the current stable version of Python is available
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at https://docs.python.org/3/. PDF, plain text, and downloadable HTML versions are
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also available at https://docs.python.org/3/download.html.
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The documentation is written in reStructuredText and processed by `the Sphinx
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documentation tool <http://sphinx-doc.org/>`__. The reStructuredText source for
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the documentation is part of the Python source distribution.
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I've never programmed before. Is there a Python tutorial?
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---------------------------------------------------------
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There are numerous tutorials and books available. The standard documentation
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includes :ref:`tutorial-index`.
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Consult `the Beginner's Guide <https://wiki.python.org/moin/BeginnersGuide>`_ to
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find information for beginning Python programmers, including lists of tutorials.
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Is there a newsgroup or mailing list devoted to Python?
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-------------------------------------------------------
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There is a newsgroup, :newsgroup:`comp.lang.python`, and a mailing list,
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`python-list <https://mail.python.org/mailman/listinfo/python-list>`_. The
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newsgroup and mailing list are gatewayed into each other -- if you can read news
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it's unnecessary to subscribe to the mailing list.
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:newsgroup:`comp.lang.python` is high-traffic, receiving hundreds of postings
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every day, and Usenet readers are often more able to cope with this volume.
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Announcements of new software releases and events can be found in
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comp.lang.python.announce, a low-traffic moderated list that receives about five
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postings per day. It's available as `the python-announce mailing list
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<https://mail.python.org/mailman/listinfo/python-announce-list>`_.
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More info about other mailing lists and newsgroups
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can be found at https://www.python.org/community/lists/.
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How do I get a beta test version of Python?
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-------------------------------------------
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Alpha and beta releases are available from https://www.python.org/downloads/. All
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releases are announced on the comp.lang.python and comp.lang.python.announce
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newsgroups and on the Python home page at https://www.python.org/; an RSS feed of
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news is available.
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You can also access the development version of Python through Git. See
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`The Python Developer's Guide <https://devguide.python.org/>`_ for details.
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How do I submit bug reports and patches for Python?
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---------------------------------------------------
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To report a bug or submit a patch, please use the Roundup installation at
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https://bugs.python.org/.
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You must have a Roundup account to report bugs; this makes it possible for us to
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contact you if we have follow-up questions. It will also enable Roundup to send
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you updates as we act on your bug. If you had previously used SourceForge to
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report bugs to Python, you can obtain your Roundup password through Roundup's
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`password reset procedure <https://bugs.python.org/user?@template=forgotten>`_.
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For more information on how Python is developed, consult `the Python Developer's
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Guide <https://devguide.python.org/>`_.
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Are there any published articles about Python that I can reference?
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-------------------------------------------------------------------
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It's probably best to cite your favorite book about Python.
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The very first article about Python was written in 1991 and is now quite
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outdated.
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Guido van Rossum and Jelke de Boer, "Interactively Testing Remote Servers
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Using the Python Programming Language", CWI Quarterly, Volume 4, Issue 4
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(December 1991), Amsterdam, pp 283--303.
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Are there any books on Python?
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------------------------------
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Yes, there are many, and more are being published. See the python.org wiki at
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https://wiki.python.org/moin/PythonBooks for a list.
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You can also search online bookstores for "Python" and filter out the Monty
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Python references; or perhaps search for "Python" and "language".
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Where in the world is www.python.org located?
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---------------------------------------------
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The Python project's infrastructure is located all over the world and is managed
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by the Python Infrastructure Team. Details `here <http://infra.psf.io>`__.
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Why is it called Python?
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------------------------
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When he began implementing Python, Guido van Rossum was also reading the
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published scripts from `"Monty Python's Flying Circus"
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<https://en.wikipedia.org/wiki/Monty_Python>`__, a BBC comedy series from the 1970s. Van Rossum
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thought he needed a name that was short, unique, and slightly mysterious, so he
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decided to call the language Python.
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Do I have to like "Monty Python's Flying Circus"?
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-------------------------------------------------
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No, but it helps. :)
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Python in the real world
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========================
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How stable is Python?
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---------------------
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Very stable. New, stable releases have been coming out roughly every 6 to 18
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months since 1991, and this seems likely to continue. Currently there are
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usually around 18 months between major releases.
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The developers issue "bugfix" releases of older versions, so the stability of
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existing releases gradually improves. Bugfix releases, indicated by a third
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component of the version number (e.g. 3.5.3, 3.6.2), are managed for stability;
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only fixes for known problems are included in a bugfix release, and it's
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guaranteed that interfaces will remain the same throughout a series of bugfix
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releases.
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The latest stable releases can always be found on the `Python download page
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<https://www.python.org/downloads/>`_. There are two production-ready versions
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of Python: 2.x and 3.x. The recommended version is 3.x, which is supported by
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most widely used libraries. Although 2.x is still widely used, `it will not
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be maintained after January 1, 2020 <https://www.python.org/dev/peps/pep-0373/>`_.
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How many people are using Python?
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---------------------------------
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There are probably tens of thousands of users, though it's difficult to obtain
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an exact count.
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Python is available for free download, so there are no sales figures, and it's
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available from many different sites and packaged with many Linux distributions,
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so download statistics don't tell the whole story either.
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The comp.lang.python newsgroup is very active, but not all Python users post to
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the group or even read it.
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Have any significant projects been done in Python?
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--------------------------------------------------
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See https://www.python.org/about/success for a list of projects that use Python.
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Consulting the proceedings for `past Python conferences
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<https://www.python.org/community/workshops/>`_ will reveal contributions from many
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different companies and organizations.
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High-profile Python projects include `the Mailman mailing list manager
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<http://www.list.org>`_ and `the Zope application server
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<http://www.zope.org>`_. Several Linux distributions, most notably `Red Hat
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<https://www.redhat.com>`_, have written part or all of their installer and
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system administration software in Python. Companies that use Python internally
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include Google, Yahoo, and Lucasfilm Ltd.
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What new developments are expected for Python in the future?
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------------------------------------------------------------
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See https://www.python.org/dev/peps/ for the Python Enhancement Proposals
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(PEPs). PEPs are design documents describing a suggested new feature for Python,
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providing a concise technical specification and a rationale. Look for a PEP
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titled "Python X.Y Release Schedule", where X.Y is a version that hasn't been
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publicly released yet.
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New development is discussed on `the python-dev mailing list
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<https://mail.python.org/mailman/listinfo/python-dev/>`_.
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Is it reasonable to propose incompatible changes to Python?
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-----------------------------------------------------------
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In general, no. There are already millions of lines of Python code around the
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world, so any change in the language that invalidates more than a very small
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fraction of existing programs has to be frowned upon. Even if you can provide a
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conversion program, there's still the problem of updating all documentation;
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many books have been written about Python, and we don't want to invalidate them
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all at a single stroke.
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Providing a gradual upgrade path is necessary if a feature has to be changed.
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:pep:`5` describes the procedure followed for introducing backward-incompatible
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changes while minimizing disruption for users.
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Is Python a good language for beginning programmers?
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----------------------------------------------------
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Yes.
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It is still common to start students with a procedural and statically typed
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language such as Pascal, C, or a subset of C++ or Java. Students may be better
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served by learning Python as their first language. Python has a very simple and
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consistent syntax and a large standard library and, most importantly, using
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Python in a beginning programming course lets students concentrate on important
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programming skills such as problem decomposition and data type design. With
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Python, students can be quickly introduced to basic concepts such as loops and
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procedures. They can probably even work with user-defined objects in their very
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first course.
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For a student who has never programmed before, using a statically typed language
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seems unnatural. It presents additional complexity that the student must master
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and slows the pace of the course. The students are trying to learn to think
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like a computer, decompose problems, design consistent interfaces, and
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encapsulate data. While learning to use a statically typed language is
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important in the long term, it is not necessarily the best topic to address in
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the students' first programming course.
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Many other aspects of Python make it a good first language. Like Java, Python
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has a large standard library so that students can be assigned programming
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projects very early in the course that *do* something. Assignments aren't
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restricted to the standard four-function calculator and check balancing
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programs. By using the standard library, students can gain the satisfaction of
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working on realistic applications as they learn the fundamentals of programming.
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Using the standard library also teaches students about code reuse. Third-party
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modules such as PyGame are also helpful in extending the students' reach.
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Python's interactive interpreter enables students to test language features
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while they're programming. They can keep a window with the interpreter running
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while they enter their program's source in another window. If they can't
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remember the methods for a list, they can do something like this::
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>>> L = []
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>>> dir(L) # doctest: +NORMALIZE_WHITESPACE
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['__add__', '__class__', '__contains__', '__delattr__', '__delitem__',
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'__dir__', '__doc__', '__eq__', '__format__', '__ge__',
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'__getattribute__', '__getitem__', '__gt__', '__hash__', '__iadd__',
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'__imul__', '__init__', '__iter__', '__le__', '__len__', '__lt__',
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'__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__',
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'__repr__', '__reversed__', '__rmul__', '__setattr__', '__setitem__',
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'__sizeof__', '__str__', '__subclasshook__', 'append', 'clear',
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'copy', 'count', 'extend', 'index', 'insert', 'pop', 'remove',
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'reverse', 'sort']
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>>> [d for d in dir(L) if '__' not in d]
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['append', 'clear', 'copy', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']
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>>> help(L.append)
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Help on built-in function append:
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<BLANKLINE>
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append(...)
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L.append(object) -> None -- append object to end
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<BLANKLINE>
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>>> L.append(1)
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>>> L
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[1]
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With the interpreter, documentation is never far from the student as they are
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programming.
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There are also good IDEs for Python. IDLE is a cross-platform IDE for Python
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that is written in Python using Tkinter. PythonWin is a Windows-specific IDE.
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Emacs users will be happy to know that there is a very good Python mode for
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Emacs. All of these programming environments provide syntax highlighting,
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auto-indenting, and access to the interactive interpreter while coding. Consult
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`the Python wiki <https://wiki.python.org/moin/PythonEditors>`_ for a full list
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of Python editing environments.
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If you want to discuss Python's use in education, you may be interested in
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joining `the edu-sig mailing list
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<https://www.python.org/community/sigs/current/edu-sig>`_.
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