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    r75363 | georg.brandl | 2009-10-11 20:31:23 +0200 (So, 11 Okt 2009) | 1 line

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+:tocdepth: 2
+
+==================
+General Python FAQ
+==================
+
+.. contents::
+
+General Information
+===================
+
+What is Python?
+---------------
+
+Python is an interpreted, interactive, object-oriented programming language.  It
+incorporates modules, exceptions, dynamic typing, very high level dynamic data
+types, and classes.  Python combines remarkable power with very clear syntax.
+It has interfaces to many system calls and libraries, as well as to various
+window systems, and is extensible in C or C++.  It is also usable as an
+extension language for applications that need a programmable interface.
+Finally, Python is portable: it runs on many Unix variants, on the Mac, and on
+PCs under MS-DOS, Windows, Windows NT, and OS/2.
+
+To find out more, start with :ref:`tutorial-index`.  The `Beginner's Guide to
+Python <http://wiki.python.org/moin/BeginnersGuide>`_ links to other
+introductory tutorials and resources for learning Python.
+
+
+What is the Python Software Foundation?
+---------------------------------------
+
+The Python Software Foundation is an independent non-profit organization that
+holds the copyright on Python versions 2.1 and newer.  The PSF's mission is to
+advance open source technology related to the Python programming language and to
+publicize the use of Python.  The PSF's home page is at
+http://www.python.org/psf/.
+
+Donations to the PSF are tax-exempt in the US.  If you use Python and find it
+helpful, please contribute via `the PSF donation page
+<http://www.python.org/psf/donations/>`_.
+
+
+Are there copyright restrictions on the use of Python?
+------------------------------------------------------
+
+You can do anything you want with the source, as long as you leave the
+copyrights in and display those copyrights in any documentation about Python
+that you produce.  If you honor the copyright rules, it's OK to use Python for
+commercial use, to sell copies of Python in source or binary form (modified or
+unmodified), or to sell products that incorporate Python in some form.  We would
+still like to know about all commercial use of Python, of course.
+
+See `the PSF license page <http://python.org/psf/license/>`_ to find further
+explanations and a link to the full text of the license.
+
+The Python logo is trademarked, and in certain cases permission is required to
+use it.  Consult `the Trademark Usage Policy
+<http://www.python.org/psf/trademarks/>`__ for more information.
+
+
+Why was Python created in the first place?
+------------------------------------------
+
+Here's a *very* brief summary of what started it all, written by Guido van
+Rossum:
+
+   I had extensive experience with implementing an interpreted language in the
+   ABC group at CWI, and from working with this group I had learned a lot about
+   language design.  This is the origin of many Python features, including the
+   use of indentation for statement grouping and the inclusion of
+   very-high-level data types (although the details are all different in
+   Python).
+
+   I had a number of gripes about the ABC language, but also liked many of its
+   features.  It was impossible to extend the ABC language (or its
+   implementation) to remedy my complaints -- in fact its lack of extensibility
+   was one of its biggest problems.  I had some experience with using Modula-2+
+   and talked with the designers of Modula-3 and read the Modula-3 report.
+   Modula-3 is the origin of the syntax and semantics used for exceptions, and
+   some other Python features.
+
+   I was working in the Amoeba distributed operating system group at CWI.  We
+   needed a better way to do system administration than by writing either C
+   programs or Bourne shell scripts, since Amoeba had its own system call
+   interface which wasn't easily accessible from the Bourne shell.  My
+   experience with error handling in Amoeba made me acutely aware of the
+   importance of exceptions as a programming language feature.
+
+   It occurred to me that a scripting language with a syntax like ABC but with
+   access to the Amoeba system calls would fill the need.  I realized that it
+   would be foolish to write an Amoeba-specific language, so I decided that I
+   needed a language that was generally extensible.
+
+   During the 1989 Christmas holidays, I had a lot of time on my hand, so I
+   decided to give it a try.  During the next year, while still mostly working
+   on it in my own time, Python was used in the Amoeba project with increasing
+   success, and the feedback from colleagues made me add many early
+   improvements.
+
+   In February 1991, after just over a year of development, I decided to post to
+   USENET.  The rest is in the ``Misc/HISTORY`` file.
+
+
+What is Python good for?
+------------------------
+
+Python is a high-level general-purpose programming language that can be applied
+to many different classes of problems.
+
+The language comes with a large standard library that covers areas such as
+string processing (regular expressions, Unicode, calculating differences between
+files), Internet protocols (HTTP, FTP, SMTP, XML-RPC, POP, IMAP, CGI
+programming), software engineering (unit testing, logging, profiling, parsing
+Python code), and operating system interfaces (system calls, filesystems, TCP/IP
+sockets).  Look at the table of contents for :ref:`library-index` to get an idea
+of what's available.  A wide variety of third-party extensions are also
+available.  Consult `the Python Package Index <http://pypi.python.org/pypi>`_ to
+find packages of interest to you.
+
+
+How does the Python version numbering scheme work?
+--------------------------------------------------
+
+Python versions are numbered A.B.C or A.B.  A is the major version number -- it
+is only incremented for really major changes in the language.  B is the minor
+version number, incremented for less earth-shattering changes.  C is the
+micro-level -- it is incremented for each bugfix release.  See :pep:`6` for more
+information about bugfix releases.
+
+Not all releases are bugfix releases.  In the run-up to a new major release, a
+series of development releases are made, denoted as alpha, beta, or release
+candidate.  Alphas are early releases in which interfaces aren't yet finalized;
+it's not unexpected to see an interface change between two alpha releases.
+Betas are more stable, preserving existing interfaces but possibly adding new
+modules, and release candidates are frozen, making no changes except as needed
+to fix critical bugs.
+
+Alpha, beta and release candidate versions have an additional suffix.  The
+suffix for an alpha version is "aN" for some small number N, the suffix for a
+beta version is "bN" for some small number N, and the suffix for a release
+candidate version is "cN" for some small number N.  In other words, all versions
+labeled 2.0aN precede the versions labeled 2.0bN, which precede versions labeled
+2.0cN, and *those* precede 2.0.
+
+You may also find version numbers with a "+" suffix, e.g. "2.2+".  These are
+unreleased versions, built directly from the Subversion trunk.  In practice,
+after a final minor release is made, the Subversion trunk is incremented to the
+next minor version, which becomes the "a0" version,
+e.g. "2.4a0".
+
+See also the documentation for ``sys.version``, ``sys.hexversion``, and
+``sys.version_info``.
+
+
+How do I obtain a copy of the Python source?
+--------------------------------------------
+
+The latest Python source distribution is always available from python.org, at
+http://www.python.org/download/.  The latest development sources can be obtained
+via anonymous Subversion at http://svn.python.org/projects/python/trunk.
+
+The source distribution is a gzipped tar file containing the complete C source,
+Sphinx-formatted documentation, Python library modules, example programs, and
+several useful pieces of freely distributable software.  The source will compile
+and run out of the box on most UNIX platforms.
+
+Consult the `Developer FAQ
+<http://www.python.org/dev/devfaq.html#subversion-svn>`__ for more information
+on getting the source code and compiling it.
+
+
+How do I get documentation on Python?
+-------------------------------------
+
+.. XXX mention py3k
+
+The standard documentation for the current stable version of Python is available
+at http://docs.python.org/.  PDF, plain text, and downloadable HTML versions are
+also available at http://docs.python.org/download/.
+
+The documentation is written in reStructuredText and processed by `the Sphinx
+documentation tool <http://sphinx.pocoo.org/>`__.  The reStructuredText source
+for the documentation is part of the Python source distribution.
+
+
+I've never programmed before. Is there a Python tutorial?
+---------------------------------------------------------
+
+There are numerous tutorials and books available.  The standard documentation
+includes :ref:`tutorial-index`.
+
+Consult `the Beginner's Guide <http://wiki.python.org/moin/BeginnersGuide>`_ to
+find information for beginning Python programmers, including lists of tutorials.
+
+
+Is there a newsgroup or mailing list devoted to Python?
+-------------------------------------------------------
+
+There is a newsgroup, :newsgroup:`comp.lang.python`, and a mailing list,
+`python-list <http://mail.python.org/mailman/listinfo/python-list>`_.  The
+newsgroup and mailing list are gatewayed into each other -- if you can read news
+it's unnecessary to subscribe to the mailing list.
+:newsgroup:`comp.lang.python` is high-traffic, receiving hundreds of postings
+every day, and Usenet readers are often more able to cope with this volume.
+
+Announcements of new software releases and events can be found in
+comp.lang.python.announce, a low-traffic moderated list that receives about five
+postings per day.  It's available as `the python-announce mailing list
+<http://mail.python.org/mailman/listinfo/python-announce-list>`_.
+
+More info about other mailing lists and newsgroups
+can be found at http://www.python.org/community/lists/.
+
+
+How do I get a beta test version of Python?
+-------------------------------------------
+
+Alpha and beta releases are available from http://www.python.org/download/.  All
+releases are announced on the comp.lang.python and comp.lang.python.announce
+newsgroups and on the Python home page at http://www.python.org/; an RSS feed of
+news is available.
+
+You can also access the development version of Python through Subversion.  See
+http://www.python.org/dev/devfaq.html#subversion-svn for details.
+
+
+How do I submit bug reports and patches for Python?
+---------------------------------------------------
+
+To report a bug or submit a patch, please use the Roundup installation at
+http://bugs.python.org/.
+
+You must have a Roundup account to report bugs; this makes it possible for us to
+contact you if we have follow-up questions.  It will also enable Roundup to send
+you updates as we act on your bug. If you had previously used SourceForge to
+report bugs to Python, you can obtain your Roundup password through Roundup's
+`password reset procedure <http://bugs.python.org/user?@template=forgotten>`_.
+
+.. XXX adapt link to dev guide
+
+For more information on how Python is developed, consult `the Python Developer's
+Guide <http://python.org/dev/>`_.
+
+
+Are there any published articles about Python that I can reference?
+-------------------------------------------------------------------
+
+It's probably best to cite your favorite book about Python.
+
+The very first article about Python was written in 1991 and is now quite
+outdated.
+
+    Guido van Rossum and Jelke de Boer, "Interactively Testing Remote Servers
+    Using the Python Programming Language", CWI Quarterly, Volume 4, Issue 4
+    (December 1991), Amsterdam, pp 283-303.
+
+
+Are there any books on Python?
+------------------------------
+
+Yes, there are many, and more are being published.  See the python.org wiki at
+http://wiki.python.org/moin/PythonBooks for a list.
+
+You can also search online bookstores for "Python" and filter out the Monty
+Python references; or perhaps search for "Python" and "language".
+
+
+Where in the world is www.python.org located?
+---------------------------------------------
+
+It's currently in Amsterdam, graciously hosted by `XS4ALL
+<http://www.xs4all.nl>`_.  Thanks to Thomas Wouters for his work in arranging
+python.org's hosting.
+
+
+Why is it called Python?
+------------------------
+
+When he began implementing Python, Guido van Rossum was also reading the
+published scripts from `"Monty Python's Flying Circus"
+<http://pythonline.com/>`__, a BBC comedy series from the 1970s.  Van Rossum
+thought he needed a name that was short, unique, and slightly mysterious, so he
+decided to call the language Python.
+
+
+Do I have to like "Monty Python's Flying Circus"?
+-------------------------------------------------
+
+No, but it helps.  :)
+
+
+Python in the real world
+========================
+
+How stable is Python?
+---------------------
+
+Very stable.  New, stable releases have been coming out roughly every 6 to 18
+months since 1991, and this seems likely to continue.  Currently there are
+usually around 18 months between major releases.
+
+The developers issue "bugfix" releases of older versions, so the stability of
+existing releases gradually improves.  Bugfix releases, indicated by a third
+component of the version number (e.g. 2.5.3, 2.6.2), are managed for stability;
+only fixes for known problems are included in a bugfix release, and it's
+guaranteed that interfaces will remain the same throughout a series of bugfix
+releases.
+
+.. XXX this gets out of date pretty often
+
+The `2.6.4 release <http://python.org/download/>`_ is recommended
+production-ready version at this point in time.  Python 3.1 is also considered
+production-ready, but may be less useful, since currently there is more third
+party software available for Python 2 than for Python 3.  Python 2 code will
+generally not run unchanged in Python 3.
+
+
+How many people are using Python?
+---------------------------------
+
+There are probably tens of thousands of users, though it's difficult to obtain
+an exact count.
+
+Python is available for free download, so there are no sales figures, and it's
+available from many different sites and packaged with many Linux distributions,
+so download statistics don't tell the whole story either.
+
+The comp.lang.python newsgroup is very active, but not all Python users post to
+the group or even read it.
+
+
+Have any significant projects been done in Python?
+--------------------------------------------------
+
+See http://python.org/about/success for a list of projects that use Python.
+Consulting the proceedings for `past Python conferences
+<http://python.org/community/workshops/>`_ will reveal contributions from many
+different companies and organizations.
+
+High-profile Python projects include `the Mailman mailing list manager
+<http://www.list.org>`_ and `the Zope application server
+<http://www.zope.org>`_.  Several Linux distributions, most notably `Red Hat
+<http://www.redhat.com>`_, have written part or all of their installer and
+system administration software in Python.  Companies that use Python internally
+include Google, Yahoo, and Lucasfilm Ltd.
+
+
+What new developments are expected for Python in the future?
+------------------------------------------------------------
+
+See http://www.python.org/dev/peps/ for the Python Enhancement Proposals
+(PEPs). PEPs are design documents describing a suggested new feature for Python,
+providing a concise technical specification and a rationale.  Look for a PEP
+titled "Python X.Y Release Schedule", where X.Y is a version that hasn't been
+publicly released yet.
+
+New development is discussed on `the python-dev mailing list
+<http://mail.python.org/mailman/listinfo/python-dev/>`_.
+
+
+Is it reasonable to propose incompatible changes to Python?
+-----------------------------------------------------------
+
+In general, no.  There are already millions of lines of Python code around the
+world, so any change in the language that invalidates more than a very small
+fraction of existing programs has to be frowned upon.  Even if you can provide a
+conversion program, there's still the problem of updating all documentation;
+many books have been written about Python, and we don't want to invalidate them
+all at a single stroke.
+
+Providing a gradual upgrade path is necessary if a feature has to be changed.
+:pep:`5` describes the procedure followed for introducing backward-incompatible
+changes while minimizing disruption for users.
+
+
+Is Python Y2K (Year 2000) Compliant?
+------------------------------------
+
+.. remove this question?
+
+As of August, 2003 no major problems have been reported and Y2K compliance seems
+to be a non-issue.
+
+Python does very few date calculations and for those it does perform relies on
+the C library functions.  Python generally represents times either as seconds
+since 1970 or as a ``(year, month, day, ...)`` tuple where the year is expressed
+with four digits, which makes Y2K bugs unlikely.  So as long as your C library
+is okay, Python should be okay.  Of course, it's possible that a particular
+application written in Python makes assumptions about 2-digit years.
+
+Because Python is available free of charge, there are no absolute guarantees.
+If there *are* unforeseen problems, liability is the user's problem rather than
+the developers', and there is nobody you can sue for damages.  The Python
+copyright notice contains the following disclaimer:
+
+    4. PSF is making Python 2.3 available to Licensee on an "AS IS"
+    basis.  PSF MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED.  BY
+    WAY OF EXAMPLE, BUT NOT LIMITATION, PSF MAKES NO AND DISCLAIMS ANY
+    REPRESENTATION OR WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR
+    PURPOSE OR THAT THE USE OF PYTHON 2.3 WILL NOT INFRINGE ANY THIRD PARTY
+    RIGHTS.
+
+    5. PSF SHALL NOT BE LIABLE TO LICENSEE OR ANY OTHER USERS OF PYTHON
+    2.3 FOR ANY INCIDENTAL, SPECIAL, OR CONSEQUENTIAL DAMAGES OR LOSS AS
+    A RESULT OF MODIFYING, DISTRIBUTING, OR OTHERWISE USING PYTHON 2.3,
+    OR ANY DERIVATIVE THEREOF, EVEN IF ADVISED OF THE POSSIBILITY THEREOF.
+
+The good news is that *if* you encounter a problem, you have full source
+available to track it down and fix it.  This is one advantage of an open source
+programming environment.
+
+
+Is Python a good language for beginning programmers?
+----------------------------------------------------
+
+Yes.
+
+It is still common to start students with a procedural and statically typed
+language such as Pascal, C, or a subset of C++ or Java.  Students may be better
+served by learning Python as their first language.  Python has a very simple and
+consistent syntax and a large standard library and, most importantly, using
+Python in a beginning programming course lets students concentrate on important
+programming skills such as problem decomposition and data type design.  With
+Python, students can be quickly introduced to basic concepts such as loops and
+procedures.  They can probably even work with user-defined objects in their very
+first course.
+
+For a student who has never programmed before, using a statically typed language
+seems unnatural.  It presents additional complexity that the student must master
+and slows the pace of the course.  The students are trying to learn to think
+like a computer, decompose problems, design consistent interfaces, and
+encapsulate data.  While learning to use a statically typed language is
+important in the long term, it is not necessarily the best topic to address in
+the students' first programming course.
+
+Many other aspects of Python make it a good first language.  Like Java, Python
+has a large standard library so that students can be assigned programming
+projects very early in the course that *do* something.  Assignments aren't
+restricted to the standard four-function calculator and check balancing
+programs.  By using the standard library, students can gain the satisfaction of
+working on realistic applications as they learn the fundamentals of programming.
+Using the standard library also teaches students about code reuse.  Third-party
+modules such as PyGame are also helpful in extending the students' reach.
+
+Python's interactive interpreter enables students to test language features
+while they're programming.  They can keep a window with the interpreter running
+while they enter their program's source in another window.  If they can't
+remember the methods for a list, they can do something like this::
+
+   >>> L = []
+   >>> dir(L)
+   ['append', 'count', 'extend', 'index', 'insert', 'pop', 'remove',
+   'reverse', 'sort']
+   >>> help(L.append)
+   Help on built-in function append:
+
+   append(...)
+       L.append(object) -- append object to end
+   >>> L.append(1)
+   >>> L
+   [1]
+
+With the interpreter, documentation is never far from the student as he's
+programming.
+
+There are also good IDEs for Python.  IDLE is a cross-platform IDE for Python
+that is written in Python using Tkinter.  PythonWin is a Windows-specific IDE.
+Emacs users will be happy to know that there is a very good Python mode for
+Emacs.  All of these programming environments provide syntax highlighting,
+auto-indenting, and access to the interactive interpreter while coding.  Consult
+http://www.python.org/editors/ for a full list of Python editing environments.
+
+If you want to discuss Python's use in education, you may be interested in
+joining `the edu-sig mailing list
+<http://python.org/community/sigs/current/edu-sig>`_.
+
+
+Upgrading Python
+================
+
+What is this bsddb185 module my application keeps complaining about?
+--------------------------------------------------------------------
+
+.. XXX remove this question?
+
+Starting with Python2.3, the distribution includes the `PyBSDDB package
+<http://pybsddb.sf.net/>` as a replacement for the old bsddb module.  It
+includes functions which provide backward compatibility at the API level, but
+requires a newer version of the underlying `Berkeley DB
+<http://www.sleepycat.com>`_ library.  Files created with the older bsddb module
+can't be opened directly using the new module.
+
+Using your old version of Python and a pair of scripts which are part of Python
+2.3 (db2pickle.py and pickle2db.py, in the Tools/scripts directory) you can
+convert your old database files to the new format.  Using your old Python
+version, run the db2pickle.py script to convert it to a pickle, e.g.::
+
+   python2.2 <pathto>/db2pickley.py database.db database.pck
+
+Rename your database file::
+
+   mv database.db olddatabase.db
+
+Now convert the pickle file to a new format database::
+
+   python <pathto>/pickle2db.py database.db database.pck
+
+The precise commands you use will vary depending on the particulars of your
+installation.  For full details about operation of these two scripts check the
+doc string at the start of each one.