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diff --git a/Doc/install/index.rst b/Doc/install/index.rst new file mode 100644 index 0000000..01f17f8 --- /dev/null +++ b/Doc/install/index.rst @@ -0,0 +1,1011 @@ +.. highlightlang:: none + +.. _install-index: + +***************************** + Installing Python Modules +***************************** + +:Author: Greg Ward +:Release: |version| +:Date: |today| + +.. % TODO: +.. % Fill in XXX comments + +.. % The audience for this document includes people who don't know anything +.. % about Python and aren't about to learn the language just in order to +.. % install and maintain it for their users, i.e. system administrators. +.. % Thus, I have to be sure to explain the basics at some point: +.. % sys.path and PYTHONPATH at least. Should probably give pointers to +.. % other docs on "import site", PYTHONSTARTUP, PYTHONHOME, etc. +.. % +.. % Finally, it might be useful to include all the material from my "Care +.. % and Feeding of a Python Installation" talk in here somewhere. Yow! + +.. topic:: Abstract + + This document describes the Python Distribution Utilities ("Distutils") from the + end-user's point-of-view, describing how to extend the capabilities of a + standard Python installation by building and installing third-party Python + modules and extensions. + + +.. _inst-intro: + +Introduction +============ + +Although Python's extensive standard library covers many programming needs, +there often comes a time when you need to add some new functionality to your +Python installation in the form of third-party modules. This might be necessary +to support your own programming, or to support an application that you want to +use and that happens to be written in Python. + +In the past, there has been little support for adding third-party modules to an +existing Python installation. With the introduction of the Python Distribution +Utilities (Distutils for short) in Python 2.0, this changed. + +This document is aimed primarily at the people who need to install third-party +Python modules: end-users and system administrators who just need to get some +Python application running, and existing Python programmers who want to add some +new goodies to their toolbox. You don't need to know Python to read this +document; there will be some brief forays into using Python's interactive mode +to explore your installation, but that's it. If you're looking for information +on how to distribute your own Python modules so that others may use them, see +the :ref:`distutils-index` manual. + + +.. _inst-trivial-install: + +Best case: trivial installation +------------------------------- + +In the best case, someone will have prepared a special version of the module +distribution you want to install that is targeted specifically at your platform +and is installed just like any other software on your platform. For example, +the module developer might make an executable installer available for Windows +users, an RPM package for users of RPM-based Linux systems (Red Hat, SuSE, +Mandrake, and many others), a Debian package for users of Debian-based Linux +systems, and so forth. + +In that case, you would download the installer appropriate to your platform and +do the obvious thing with it: run it if it's an executable installer, ``rpm +--install`` it if it's an RPM, etc. You don't need to run Python or a setup +script, you don't need to compile anything---you might not even need to read any +instructions (although it's always a good idea to do so anyways). + +Of course, things will not always be that easy. You might be interested in a +module distribution that doesn't have an easy-to-use installer for your +platform. In that case, you'll have to start with the source distribution +released by the module's author/maintainer. Installing from a source +distribution is not too hard, as long as the modules are packaged in the +standard way. The bulk of this document is about building and installing +modules from standard source distributions. + + +.. _inst-new-standard: + +The new standard: Distutils +--------------------------- + +If you download a module source distribution, you can tell pretty quickly if it +was packaged and distributed in the standard way, i.e. using the Distutils. +First, the distribution's name and version number will be featured prominently +in the name of the downloaded archive, e.g. :file:`foo-1.0.tar.gz` or +:file:`widget-0.9.7.zip`. Next, the archive will unpack into a similarly-named +directory: :file:`foo-1.0` or :file:`widget-0.9.7`. Additionally, the +distribution will contain a setup script :file:`setup.py`, and a file named +:file:`README.txt` or possibly just :file:`README`, which should explain that +building and installing the module distribution is a simple matter of running :: + + python setup.py install + +If all these things are true, then you already know how to build and install the +modules you've just downloaded: Run the command above. Unless you need to +install things in a non-standard way or customize the build process, you don't +really need this manual. Or rather, the above command is everything you need to +get out of this manual. + + +.. _inst-standard-install: + +Standard Build and Install +========================== + +As described in section :ref:`inst-new-standard`, building and installing a module +distribution using the Distutils is usually one simple command:: + + python setup.py install + +On Unix, you'd run this command from a shell prompt; on Windows, you have to +open a command prompt window ("DOS box") and do it there; on Mac OS X, you open +a :command:`Terminal` window to get a shell prompt. + + +.. _inst-platform-variations: + +Platform variations +------------------- + +You should always run the setup command from the distribution root directory, +i.e. the top-level subdirectory that the module source distribution unpacks +into. For example, if you've just downloaded a module source distribution +:file:`foo-1.0.tar.gz` onto a Unix system, the normal thing to do is:: + + gunzip -c foo-1.0.tar.gz | tar xf - # unpacks into directory foo-1.0 + cd foo-1.0 + python setup.py install + +On Windows, you'd probably download :file:`foo-1.0.zip`. If you downloaded the +archive file to :file:`C:\\Temp`, then it would unpack into +:file:`C:\\Temp\\foo-1.0`; you can use either a archive manipulator with a +graphical user interface (such as WinZip) or a command-line tool (such as +:program:`unzip` or :program:`pkunzip`) to unpack the archive. Then, open a +command prompt window ("DOS box"), and run:: + + cd c:\Temp\foo-1.0 + python setup.py install + + +.. _inst-splitting-up: + +Splitting the job up +-------------------- + +Running ``setup.py install`` builds and installs all modules in one run. If you +prefer to work incrementally---especially useful if you want to customize the +build process, or if things are going wrong---you can use the setup script to do +one thing at a time. This is particularly helpful when the build and install +will be done by different users---for example, you might want to build a module +distribution and hand it off to a system administrator for installation (or do +it yourself, with super-user privileges). + +For example, you can build everything in one step, and then install everything +in a second step, by invoking the setup script twice:: + + python setup.py build + python setup.py install + +If you do this, you will notice that running the :command:`install` command +first runs the :command:`build` command, which---in this case---quickly notices +that it has nothing to do, since everything in the :file:`build` directory is +up-to-date. + +You may not need this ability to break things down often if all you do is +install modules downloaded off the 'net, but it's very handy for more advanced +tasks. If you get into distributing your own Python modules and extensions, +you'll run lots of individual Distutils commands on their own. + + +.. _inst-how-build-works: + +How building works +------------------ + +As implied above, the :command:`build` command is responsible for putting the +files to install into a *build directory*. By default, this is :file:`build` +under the distribution root; if you're excessively concerned with speed, or want +to keep the source tree pristine, you can change the build directory with the +:option:`--build-base` option. For example:: + + python setup.py build --build-base=/tmp/pybuild/foo-1.0 + +(Or you could do this permanently with a directive in your system or personal +Distutils configuration file; see section :ref:`inst-config-files`.) Normally, this +isn't necessary. + +The default layout for the build tree is as follows:: + + --- build/ --- lib/ + or + --- build/ --- lib.<plat>/ + temp.<plat>/ + +where ``<plat>`` expands to a brief description of the current OS/hardware +platform and Python version. The first form, with just a :file:`lib` directory, +is used for "pure module distributions"---that is, module distributions that +include only pure Python modules. If a module distribution contains any +extensions (modules written in C/C++), then the second form, with two ``<plat>`` +directories, is used. In that case, the :file:`temp.{plat}` directory holds +temporary files generated by the compile/link process that don't actually get +installed. In either case, the :file:`lib` (or :file:`lib.{plat}`) directory +contains all Python modules (pure Python and extensions) that will be installed. + +In the future, more directories will be added to handle Python scripts, +documentation, binary executables, and whatever else is needed to handle the job +of installing Python modules and applications. + + +.. _inst-how-install-works: + +How installation works +---------------------- + +After the :command:`build` command runs (whether you run it explicitly, or the +:command:`install` command does it for you), the work of the :command:`install` +command is relatively simple: all it has to do is copy everything under +:file:`build/lib` (or :file:`build/lib.{plat}`) to your chosen installation +directory. + +If you don't choose an installation directory---i.e., if you just run ``setup.py +install``\ ---then the :command:`install` command installs to the standard +location for third-party Python modules. This location varies by platform and +by how you built/installed Python itself. On Unix (and Mac OS X, which is also +Unix-based), it also depends on whether the module distribution being installed +is pure Python or contains extensions ("non-pure"): + ++-----------------+-----------------------------------------------------+--------------------------------------------------+-------+ +| Platform | Standard installation location | Default value | Notes | ++=================+=====================================================+==================================================+=======+ +| Unix (pure) | :file:`{prefix}/lib/python{X.Y}/site-packages` | :file:`/usr/local/lib/python{X.Y}/site-packages` | \(1) | ++-----------------+-----------------------------------------------------+--------------------------------------------------+-------+ +| Unix (non-pure) | :file:`{exec-prefix}/lib/python{X.Y}/site-packages` | :file:`/usr/local/lib/python{X.Y}/site-packages` | \(1) | ++-----------------+-----------------------------------------------------+--------------------------------------------------+-------+ +| Windows | :file:`{prefix}` | :file:`C:\\Python` | \(2) | ++-----------------+-----------------------------------------------------+--------------------------------------------------+-------+ + +Notes: + +(1) + Most Linux distributions include Python as a standard part of the system, so + :file:`{prefix}` and :file:`{exec-prefix}` are usually both :file:`/usr` on + Linux. If you build Python yourself on Linux (or any Unix-like system), the + default :file:`{prefix}` and :file:`{exec-prefix}` are :file:`/usr/local`. + +(2) + The default installation directory on Windows was :file:`C:\\Program + Files\\Python` under Python 1.6a1, 1.5.2, and earlier. + +:file:`{prefix}` and :file:`{exec-prefix}` stand for the directories that Python +is installed to, and where it finds its libraries at run-time. They are always +the same under Windows, and very often the same under Unix and Mac OS X. You +can find out what your Python installation uses for :file:`{prefix}` and +:file:`{exec-prefix}` by running Python in interactive mode and typing a few +simple commands. Under Unix, just type ``python`` at the shell prompt. Under +Windows, choose :menuselection:`Start --> Programs --> Python X.Y --> +Python (command line)`. Once the interpreter is started, you type Python code +at the prompt. For example, on my Linux system, I type the three Python +statements shown below, and get the output as shown, to find out my +:file:`{prefix}` and :file:`{exec-prefix}`:: + + Python 2.4 (#26, Aug 7 2004, 17:19:02) + Type "help", "copyright", "credits" or "license" for more information. + >>> import sys + >>> sys.prefix + '/usr' + >>> sys.exec_prefix + '/usr' + +If you don't want to install modules to the standard location, or if you don't +have permission to write there, then you need to read about alternate +installations in section :ref:`inst-alt-install`. If you want to customize your +installation directories more heavily, see section :ref:`inst-custom-install` on +custom installations. + + +.. _inst-alt-install: + +Alternate Installation +====================== + +Often, it is necessary or desirable to install modules to a location other than +the standard location for third-party Python modules. For example, on a Unix +system you might not have permission to write to the standard third-party module +directory. Or you might wish to try out a module before making it a standard +part of your local Python installation. This is especially true when upgrading +a distribution already present: you want to make sure your existing base of +scripts still works with the new version before actually upgrading. + +The Distutils :command:`install` command is designed to make installing module +distributions to an alternate location simple and painless. The basic idea is +that you supply a base directory for the installation, and the +:command:`install` command picks a set of directories (called an *installation +scheme*) under this base directory in which to install files. The details +differ across platforms, so read whichever of the following sections applies to +you. + + +.. _inst-alt-install-prefix: + +Alternate installation: the home scheme +--------------------------------------- + +The idea behind the "home scheme" is that you build and maintain a personal +stash of Python modules. This scheme's name is derived from the idea of a +"home" directory on Unix, since it's not unusual for a Unix user to make their +home directory have a layout similar to :file:`/usr/` or :file:`/usr/local/`. +This scheme can be used by anyone, regardless of the operating system their +installing for. + +Installing a new module distribution is as simple as :: + + python setup.py install --home=<dir> + +where you can supply any directory you like for the :option:`--home` option. On +Unix, lazy typists can just type a tilde (``~``); the :command:`install` command +will expand this to your home directory:: + + python setup.py install --home=~ + +The :option:`--home` option defines the installation base directory. Files are +installed to the following directories under the installation base as follows: + ++------------------------------+---------------------------+-----------------------------+ +| Type of file | Installation Directory | Override option | ++==============================+===========================+=============================+ +| pure module distribution | :file:`{home}/lib/python` | :option:`--install-purelib` | ++------------------------------+---------------------------+-----------------------------+ +| non-pure module distribution | :file:`{home}/lib/python` | :option:`--install-platlib` | ++------------------------------+---------------------------+-----------------------------+ +| scripts | :file:`{home}/bin` | :option:`--install-scripts` | ++------------------------------+---------------------------+-----------------------------+ +| data | :file:`{home}/share` | :option:`--install-data` | ++------------------------------+---------------------------+-----------------------------+ + +.. versionchanged:: 2.4 + The :option:`--home` option used to be supported only on Unix. + + +.. _inst-alt-install-home: + +Alternate installation: Unix (the prefix scheme) +------------------------------------------------ + +The "prefix scheme" is useful when you wish to use one Python installation to +perform the build/install (i.e., to run the setup script), but install modules +into the third-party module directory of a different Python installation (or +something that looks like a different Python installation). If this sounds a +trifle unusual, it is---that's why the "home scheme" comes first. However, +there are at least two known cases where the prefix scheme will be useful. + +First, consider that many Linux distributions put Python in :file:`/usr`, rather +than the more traditional :file:`/usr/local`. This is entirely appropriate, +since in those cases Python is part of "the system" rather than a local add-on. +However, if you are installing Python modules from source, you probably want +them to go in :file:`/usr/local/lib/python2.{X}` rather than +:file:`/usr/lib/python2.{X}`. This can be done with :: + + /usr/bin/python setup.py install --prefix=/usr/local + +Another possibility is a network filesystem where the name used to write to a +remote directory is different from the name used to read it: for example, the +Python interpreter accessed as :file:`/usr/local/bin/python` might search for +modules in :file:`/usr/local/lib/python2.{X}`, but those modules would have to +be installed to, say, :file:`/mnt/{@server}/export/lib/python2.{X}`. This could +be done with :: + + /usr/local/bin/python setup.py install --prefix=/mnt/@server/export + +In either case, the :option:`--prefix` option defines the installation base, and +the :option:`--exec-prefix` option defines the platform-specific installation +base, which is used for platform-specific files. (Currently, this just means +non-pure module distributions, but could be expanded to C libraries, binary +executables, etc.) If :option:`--exec-prefix` is not supplied, it defaults to +:option:`--prefix`. Files are installed as follows: + ++------------------------------+-----------------------------------------------------+-----------------------------+ +| Type of file | Installation Directory | Override option | ++==============================+=====================================================+=============================+ +| pure module distribution | :file:`{prefix}/lib/python{X.Y}/site-packages` | :option:`--install-purelib` | ++------------------------------+-----------------------------------------------------+-----------------------------+ +| non-pure module distribution | :file:`{exec-prefix}/lib/python{X.Y}/site-packages` | :option:`--install-platlib` | ++------------------------------+-----------------------------------------------------+-----------------------------+ +| scripts | :file:`{prefix}/bin` | :option:`--install-scripts` | ++------------------------------+-----------------------------------------------------+-----------------------------+ +| data | :file:`{prefix}/share` | :option:`--install-data` | ++------------------------------+-----------------------------------------------------+-----------------------------+ + +There is no requirement that :option:`--prefix` or :option:`--exec-prefix` +actually point to an alternate Python installation; if the directories listed +above do not already exist, they are created at installation time. + +Incidentally, the real reason the prefix scheme is important is simply that a +standard Unix installation uses the prefix scheme, but with :option:`--prefix` +and :option:`--exec-prefix` supplied by Python itself as ``sys.prefix`` and +``sys.exec_prefix``. Thus, you might think you'll never use the prefix scheme, +but every time you run ``python setup.py install`` without any other options, +you're using it. + +Note that installing extensions to an alternate Python installation has no +effect on how those extensions are built: in particular, the Python header files +(:file:`Python.h` and friends) installed with the Python interpreter used to run +the setup script will be used in compiling extensions. It is your +responsibility to ensure that the interpreter used to run extensions installed +in this way is compatible with the interpreter used to build them. The best way +to do this is to ensure that the two interpreters are the same version of Python +(possibly different builds, or possibly copies of the same build). (Of course, +if your :option:`--prefix` and :option:`--exec-prefix` don't even point to an +alternate Python installation, this is immaterial.) + + +.. _inst-alt-install-windows: + +Alternate installation: Windows (the prefix scheme) +--------------------------------------------------- + +Windows has no concept of a user's home directory, and since the standard Python +installation under Windows is simpler than under Unix, the :option:`--prefix` +option has traditionally been used to install additional packages in separate +locations on Windows. :: + + python setup.py install --prefix="\Temp\Python" + +to install modules to the :file:`\\Temp\\Python` directory on the current drive. + +The installation base is defined by the :option:`--prefix` option; the +:option:`--exec-prefix` option is not supported under Windows. Files are +installed as follows: + ++------------------------------+---------------------------+-----------------------------+ +| Type of file | Installation Directory | Override option | ++==============================+===========================+=============================+ +| pure module distribution | :file:`{prefix}` | :option:`--install-purelib` | ++------------------------------+---------------------------+-----------------------------+ +| non-pure module distribution | :file:`{prefix}` | :option:`--install-platlib` | ++------------------------------+---------------------------+-----------------------------+ +| scripts | :file:`{prefix}\\Scripts` | :option:`--install-scripts` | ++------------------------------+---------------------------+-----------------------------+ +| data | :file:`{prefix}\\Data` | :option:`--install-data` | ++------------------------------+---------------------------+-----------------------------+ + + +.. _inst-custom-install: + +Custom Installation +=================== + +Sometimes, the alternate installation schemes described in section +:ref:`inst-alt-install` just don't do what you want. You might want to tweak just +one or two directories while keeping everything under the same base directory, +or you might want to completely redefine the installation scheme. In either +case, you're creating a *custom installation scheme*. + +You probably noticed the column of "override options" in the tables describing +the alternate installation schemes above. Those options are how you define a +custom installation scheme. These override options can be relative, absolute, +or explicitly defined in terms of one of the installation base directories. +(There are two installation base directories, and they are normally the same--- +they only differ when you use the Unix "prefix scheme" and supply different +:option:`--prefix` and :option:`--exec-prefix` options.) + +For example, say you're installing a module distribution to your home directory +under Unix---but you want scripts to go in :file:`~/scripts` rather than +:file:`~/bin`. As you might expect, you can override this directory with the +:option:`--install-scripts` option; in this case, it makes most sense to supply +a relative path, which will be interpreted relative to the installation base +directory (your home directory, in this case):: + + python setup.py install --home=~ --install-scripts=scripts + +Another Unix example: suppose your Python installation was built and installed +with a prefix of :file:`/usr/local/python`, so under a standard installation +scripts will wind up in :file:`/usr/local/python/bin`. If you want them in +:file:`/usr/local/bin` instead, you would supply this absolute directory for the +:option:`--install-scripts` option:: + + python setup.py install --install-scripts=/usr/local/bin + +(This performs an installation using the "prefix scheme," where the prefix is +whatever your Python interpreter was installed with--- :file:`/usr/local/python` +in this case.) + +If you maintain Python on Windows, you might want third-party modules to live in +a subdirectory of :file:`{prefix}`, rather than right in :file:`{prefix}` +itself. This is almost as easy as customizing the script installation directory +---you just have to remember that there are two types of modules to worry about, +pure modules and non-pure modules (i.e., modules from a non-pure distribution). +For example:: + + python setup.py install --install-purelib=Site --install-platlib=Site + +The specified installation directories are relative to :file:`{prefix}`. Of +course, you also have to ensure that these directories are in Python's module +search path, such as by putting a :file:`.pth` file in :file:`{prefix}`. See +section :ref:`inst-search-path` to find out how to modify Python's search path. + +If you want to define an entire installation scheme, you just have to supply all +of the installation directory options. The recommended way to do this is to +supply relative paths; for example, if you want to maintain all Python +module-related files under :file:`python` in your home directory, and you want a +separate directory for each platform that you use your home directory from, you +might define the following installation scheme:: + + python setup.py install --home=~ \ + --install-purelib=python/lib \ + --install-platlib=python/lib.$PLAT \ + --install-scripts=python/scripts + --install-data=python/data + +or, equivalently, + +.. % $ % -- bow to font-lock + +:: + + python setup.py install --home=~/python \ + --install-purelib=lib \ + --install-platlib='lib.$PLAT' \ + --install-scripts=scripts + --install-data=data + +``$PLAT`` is not (necessarily) an environment variable---it will be expanded by +the Distutils as it parses your command line options, just as it does when +parsing your configuration file(s). + +.. % $ % -- bow to font-lock + +Obviously, specifying the entire installation scheme every time you install a +new module distribution would be very tedious. Thus, you can put these options +into your Distutils config file (see section :ref:`inst-config-files`):: + + [install] + install-base=$HOME + install-purelib=python/lib + install-platlib=python/lib.$PLAT + install-scripts=python/scripts + install-data=python/data + +or, equivalently, :: + + [install] + install-base=$HOME/python + install-purelib=lib + install-platlib=lib.$PLAT + install-scripts=scripts + install-data=data + +Note that these two are *not* equivalent if you supply a different installation +base directory when you run the setup script. For example, :: + + python setup.py install --install-base=/tmp + +would install pure modules to :file:`{/tmp/python/lib}` in the first case, and +to :file:`{/tmp/lib}` in the second case. (For the second case, you probably +want to supply an installation base of :file:`/tmp/python`.) + +You probably noticed the use of ``$HOME`` and ``$PLAT`` in the sample +configuration file input. These are Distutils configuration variables, which +bear a strong resemblance to environment variables. In fact, you can use +environment variables in config files on platforms that have such a notion but +the Distutils additionally define a few extra variables that may not be in your +environment, such as ``$PLAT``. (And of course, on systems that don't have +environment variables, such as Mac OS 9, the configuration variables supplied by +the Distutils are the only ones you can use.) See section :ref:`inst-config-files` +for details. + +.. % XXX need some Windows examples---when would custom +.. % installation schemes be needed on those platforms? + +.. % XXX I'm not sure where this section should go. + + +.. _inst-search-path: + +Modifying Python's Search Path +------------------------------ + +When the Python interpreter executes an :keyword:`import` statement, it searches +for both Python code and extension modules along a search path. A default value +for the path is configured into the Python binary when the interpreter is built. +You can determine the path by importing the :mod:`sys` module and printing the +value of ``sys.path``. :: + + $ python + Python 2.2 (#11, Oct 3 2002, 13:31:27) + [GCC 2.96 20000731 (Red Hat Linux 7.3 2.96-112)] on linux2 + Type ``help'', ``copyright'', ``credits'' or ``license'' for more information. + >>> import sys + >>> sys.path + ['', '/usr/local/lib/python2.3', '/usr/local/lib/python2.3/plat-linux2', + '/usr/local/lib/python2.3/lib-tk', '/usr/local/lib/python2.3/lib-dynload', + '/usr/local/lib/python2.3/site-packages'] + >>> + +The null string in ``sys.path`` represents the current working directory. + +.. % $ <-- bow to font-lock + +The expected convention for locally installed packages is to put them in the +:file:`{...}/site-packages/` directory, but you may want to install Python +modules into some arbitrary directory. For example, your site may have a +convention of keeping all software related to the web server under :file:`/www`. +Add-on Python modules might then belong in :file:`/www/python`, and in order to +import them, this directory must be added to ``sys.path``. There are several +different ways to add the directory. + +The most convenient way is to add a path configuration file to a directory +that's already on Python's path, usually to the :file:`.../site-packages/` +directory. Path configuration files have an extension of :file:`.pth`, and each +line must contain a single path that will be appended to ``sys.path``. (Because +the new paths are appended to ``sys.path``, modules in the added directories +will not override standard modules. This means you can't use this mechanism for +installing fixed versions of standard modules.) + +Paths can be absolute or relative, in which case they're relative to the +directory containing the :file:`.pth` file. Any directories added to the search +path will be scanned in turn for :file:`.pth` files. See `site module +documentation <http://www.python.org/dev/doc/devel/lib/module-site.html>`_ for +more information. + +A slightly less convenient way is to edit the :file:`site.py` file in Python's +standard library, and modify ``sys.path``. :file:`site.py` is automatically +imported when the Python interpreter is executed, unless the :option:`-S` switch +is supplied to suppress this behaviour. So you could simply edit +:file:`site.py` and add two lines to it:: + + import sys + sys.path.append('/www/python/') + +However, if you reinstall the same major version of Python (perhaps when +upgrading from 2.2 to 2.2.2, for example) :file:`site.py` will be overwritten by +the stock version. You'd have to remember that it was modified and save a copy +before doing the installation. + +There are two environment variables that can modify ``sys.path``. +:envvar:`PYTHONHOME` sets an alternate value for the prefix of the Python +installation. For example, if :envvar:`PYTHONHOME` is set to ``/www/python``, +the search path will be set to ``['', '/www/python/lib/pythonX.Y/', +'/www/python/lib/pythonX.Y/plat-linux2', ...]``. + +The :envvar:`PYTHONPATH` variable can be set to a list of paths that will be +added to the beginning of ``sys.path``. For example, if :envvar:`PYTHONPATH` is +set to ``/www/python:/opt/py``, the search path will begin with +``['/www/python', '/opt/py']``. (Note that directories must exist in order to +be added to ``sys.path``; the :mod:`site` module removes paths that don't +exist.) + +Finally, ``sys.path`` is just a regular Python list, so any Python application +can modify it by adding or removing entries. + + +.. _inst-config-files: + +Distutils Configuration Files +============================= + +As mentioned above, you can use Distutils configuration files to record personal +or site preferences for any Distutils options. That is, any option to any +command can be stored in one of two or three (depending on your platform) +configuration files, which will be consulted before the command-line is parsed. +This means that configuration files will override default values, and the +command-line will in turn override configuration files. Furthermore, if +multiple configuration files apply, values from "earlier" files are overridden +by "later" files. + + +.. _inst-config-filenames: + +Location and names of config files +---------------------------------- + +The names and locations of the configuration files vary slightly across +platforms. On Unix and Mac OS X, the three configuration files (in the order +they are processed) are: + ++--------------+----------------------------------------------------------+-------+ +| Type of file | Location and filename | Notes | ++==============+==========================================================+=======+ +| system | :file:`{prefix}/lib/python{ver}/distutils/distutils.cfg` | \(1) | ++--------------+----------------------------------------------------------+-------+ +| personal | :file:`$HOME/.pydistutils.cfg` | \(2) | ++--------------+----------------------------------------------------------+-------+ +| local | :file:`setup.cfg` | \(3) | ++--------------+----------------------------------------------------------+-------+ + +And on Windows, the configuration files are: + ++--------------+-------------------------------------------------+-------+ +| Type of file | Location and filename | Notes | ++==============+=================================================+=======+ +| system | :file:`{prefix}\\Lib\\distutils\\distutils.cfg` | \(4) | ++--------------+-------------------------------------------------+-------+ +| personal | :file:`%HOME%\\pydistutils.cfg` | \(5) | ++--------------+-------------------------------------------------+-------+ +| local | :file:`setup.cfg` | \(3) | ++--------------+-------------------------------------------------+-------+ + +Notes: + +(1) + Strictly speaking, the system-wide configuration file lives in the directory + where the Distutils are installed; under Python 1.6 and later on Unix, this is + as shown. For Python 1.5.2, the Distutils will normally be installed to + :file:`{prefix}/lib/python1.5/site-packages/distutils`, so the system + configuration file should be put there under Python 1.5.2. + +(2) + On Unix, if the :envvar:`HOME` environment variable is not defined, the user's + home directory will be determined with the :func:`getpwuid` function from the + standard :mod:`pwd` module. + +(3) + I.e., in the current directory (usually the location of the setup script). + +(4) + (See also note (1).) Under Python 1.6 and later, Python's default "installation + prefix" is :file:`C:\\Python`, so the system configuration file is normally + :file:`C:\\Python\\Lib\\distutils\\distutils.cfg`. Under Python 1.5.2, the + default prefix was :file:`C:\\Program Files\\Python`, and the Distutils were not + part of the standard library---so the system configuration file would be + :file:`C:\\Program Files\\Python\\distutils\\distutils.cfg` in a standard Python + 1.5.2 installation under Windows. + +(5) + On Windows, if the :envvar:`HOME` environment variable is not defined, no + personal configuration file will be found or used. (In other words, the + Distutils make no attempt to guess your home directory on Windows.) + + +.. _inst-config-syntax: + +Syntax of config files +---------------------- + +The Distutils configuration files all have the same syntax. The config files +are grouped into sections. There is one section for each Distutils command, +plus a ``global`` section for global options that affect every command. Each +section consists of one option per line, specified as ``option=value``. + +For example, the following is a complete config file that just forces all +commands to run quietly by default:: + + [global] + verbose=0 + +If this is installed as the system config file, it will affect all processing of +any Python module distribution by any user on the current system. If it is +installed as your personal config file (on systems that support them), it will +affect only module distributions processed by you. And if it is used as the +:file:`setup.cfg` for a particular module distribution, it affects only that +distribution. + +You could override the default "build base" directory and make the +:command:`build\*` commands always forcibly rebuild all files with the +following:: + + [build] + build-base=blib + force=1 + +which corresponds to the command-line arguments :: + + python setup.py build --build-base=blib --force + +except that including the :command:`build` command on the command-line means +that command will be run. Including a particular command in config files has no +such implication; it only means that if the command is run, the options in the +config file will apply. (Or if other commands that derive values from it are +run, they will use the values in the config file.) + +You can find out the complete list of options for any command using the +:option:`--help` option, e.g.:: + + python setup.py build --help + +and you can find out the complete list of global options by using +:option:`--help` without a command:: + + python setup.py --help + +See also the "Reference" section of the "Distributing Python Modules" manual. + + +.. _inst-building-ext: + +Building Extensions: Tips and Tricks +==================================== + +Whenever possible, the Distutils try to use the configuration information made +available by the Python interpreter used to run the :file:`setup.py` script. +For example, the same compiler and linker flags used to compile Python will also +be used for compiling extensions. Usually this will work well, but in +complicated situations this might be inappropriate. This section discusses how +to override the usual Distutils behaviour. + + +.. _inst-tweak-flags: + +Tweaking compiler/linker flags +------------------------------ + +Compiling a Python extension written in C or C++ will sometimes require +specifying custom flags for the compiler and linker in order to use a particular +library or produce a special kind of object code. This is especially true if the +extension hasn't been tested on your platform, or if you're trying to +cross-compile Python. + +In the most general case, the extension author might have foreseen that +compiling the extensions would be complicated, and provided a :file:`Setup` file +for you to edit. This will likely only be done if the module distribution +contains many separate extension modules, or if they often require elaborate +sets of compiler flags in order to work. + +A :file:`Setup` file, if present, is parsed in order to get a list of extensions +to build. Each line in a :file:`Setup` describes a single module. Lines have +the following structure:: + + module ... [sourcefile ...] [cpparg ...] [library ...] + + +Let's examine each of the fields in turn. + +* *module* is the name of the extension module to be built, and should be a + valid Python identifier. You can't just change this in order to rename a module + (edits to the source code would also be needed), so this should be left alone. + +* *sourcefile* is anything that's likely to be a source code file, at least + judging by the filename. Filenames ending in :file:`.c` are assumed to be + written in C, filenames ending in :file:`.C`, :file:`.cc`, and :file:`.c++` are + assumed to be C++, and filenames ending in :file:`.m` or :file:`.mm` are assumed + to be in Objective C. + +* *cpparg* is an argument for the C preprocessor, and is anything starting with + :option:`-I`, :option:`-D`, :option:`-U` or :option:`-C`. + +* *library* is anything ending in :file:`.a` or beginning with :option:`-l` or + :option:`-L`. + +If a particular platform requires a special library on your platform, you can +add it by editing the :file:`Setup` file and running ``python setup.py build``. +For example, if the module defined by the line :: + + foo foomodule.c + +must be linked with the math library :file:`libm.a` on your platform, simply add +:option:`-lm` to the line:: + + foo foomodule.c -lm + +Arbitrary switches intended for the compiler or the linker can be supplied with +the :option:`-Xcompiler` *arg* and :option:`-Xlinker` *arg* options:: + + foo foomodule.c -Xcompiler -o32 -Xlinker -shared -lm + +The next option after :option:`-Xcompiler` and :option:`-Xlinker` will be +appended to the proper command line, so in the above example the compiler will +be passed the :option:`-o32` option, and the linker will be passed +:option:`-shared`. If a compiler option requires an argument, you'll have to +supply multiple :option:`-Xcompiler` options; for example, to pass ``-x c++`` +the :file:`Setup` file would have to contain ``-Xcompiler -x -Xcompiler c++``. + +Compiler flags can also be supplied through setting the :envvar:`CFLAGS` +environment variable. If set, the contents of :envvar:`CFLAGS` will be added to +the compiler flags specified in the :file:`Setup` file. + + +.. _inst-non-ms-compilers: + +Using non-Microsoft compilers on Windows +---------------------------------------- + +.. sectionauthor:: Rene Liebscher <R.Liebscher@gmx.de> + + + +Borland C++ +^^^^^^^^^^^ + +This subsection describes the necessary steps to use Distutils with the Borland +C++ compiler version 5.5. First you have to know that Borland's object file +format (OMF) is different from the format used by the Python version you can +download from the Python or ActiveState Web site. (Python is built with +Microsoft Visual C++, which uses COFF as the object file format.) For this +reason you have to convert Python's library :file:`python25.lib` into the +Borland format. You can do this as follows: + +.. % Should we mention that users have to create cfg-files for the compiler? +.. % see also http://community.borland.com/article/0,1410,21205,00.html + +:: + + coff2omf python25.lib python25_bcpp.lib + +The :file:`coff2omf` program comes with the Borland compiler. The file +:file:`python25.lib` is in the :file:`Libs` directory of your Python +installation. If your extension uses other libraries (zlib, ...) you have to +convert them too. + +The converted files have to reside in the same directories as the normal +libraries. + +How does Distutils manage to use these libraries with their changed names? If +the extension needs a library (eg. :file:`foo`) Distutils checks first if it +finds a library with suffix :file:`_bcpp` (eg. :file:`foo_bcpp.lib`) and then +uses this library. In the case it doesn't find such a special library it uses +the default name (:file:`foo.lib`.) [#]_ + +To let Distutils compile your extension with Borland C++ you now have to type:: + + python setup.py build --compiler=bcpp + +If you want to use the Borland C++ compiler as the default, you could specify +this in your personal or system-wide configuration file for Distutils (see +section :ref:`inst-config-files`.) + + +.. seealso:: + + `C++Builder Compiler <http://www.borland.com/bcppbuilder/freecompiler/>`_ + Information about the free C++ compiler from Borland, including links to the + download pages. + + `Creating Python Extensions Using Borland's Free Compiler <http://www.cyberus.ca/~g_will/pyExtenDL.shtml>`_ + Document describing how to use Borland's free command-line C++ compiler to build + Python. + + +GNU C / Cygwin / MinGW +^^^^^^^^^^^^^^^^^^^^^^ + +These instructions only apply if you're using a version of Python prior to +2.4.1 with a MinGW prior to 3.0.0 (with binutils-2.13.90-20030111-1). + +This section describes the necessary steps to use Distutils with the GNU C/C++ +compilers in their Cygwin and MinGW distributions. [#]_ For a Python interpreter +that was built with Cygwin, everything should work without any of these +following steps. + +These compilers require some special libraries. This task is more complex than +for Borland's C++, because there is no program to convert the library. First +you have to create a list of symbols which the Python DLL exports. (You can find +a good program for this task at +http://starship.python.net/crew/kernr/mingw32/Notes.html, see at PExports 0.42h +there.) + +.. % I don't understand what the next line means. --amk +.. % (inclusive the references on data structures.) + +:: + + pexports python25.dll >python25.def + +The location of an installed :file:`python25.dll` will depend on the +installation options and the version and language of Windows. In a "just for +me" installation, it will appear in the root of the installation directory. In +a shared installation, it will be located in the system directory. + +Then you can create from these information an import library for gcc. :: + + /cygwin/bin/dlltool --dllname python25.dll --def python25.def --output-lib libpython25.a + +The resulting library has to be placed in the same directory as +:file:`python25.lib`. (Should be the :file:`libs` directory under your Python +installation directory.) + +If your extension uses other libraries (zlib,...) you might have to convert +them too. The converted files have to reside in the same directories as the +normal libraries do. + +To let Distutils compile your extension with Cygwin you now have to type :: + + python setup.py build --compiler=cygwin + +and for Cygwin in no-cygwin mode [#]_ or for MinGW type:: + + python setup.py build --compiler=mingw32 + +If you want to use any of these options/compilers as default, you should +consider to write it in your personal or system-wide configuration file for +Distutils (see section :ref:`inst-config-files`.) + + +.. seealso:: + + `Building Python modules on MS Windows platform with MinGW <http://www.zope.org/Members/als/tips/win32_mingw_modules>`_ + Information about building the required libraries for the MinGW environment. + + http://pyopengl.sourceforge.net/ftp/win32-stuff/ + Converted import libraries in Cygwin/MinGW and Borland format, and a script to + create the registry entries needed for Distutils to locate the built Python. + +.. rubric:: Footnotes + +.. [#] This also means you could replace all existing COFF-libraries with OMF-libraries + of the same name. + +.. [#] Check http://sources.redhat.com/cygwin/ and http://www.mingw.org/ for more + information + +.. [#] Then you have no POSIX emulation available, but you also don't need + :file:`cygwin1.dll`. |