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diff --git a/Doc/install/install.rst b/Doc/install/install.rst new file mode 100644 index 0000000000..33f3e9c2c3 --- /dev/null +++ b/Doc/install/install.rst @@ -0,0 +1,1117 @@ +.. highlightlang:: none + +==================================== +Installing Python projects: overwiew +==================================== + +.. _packaging-install-intro: + +Introduction +============ + +Although Python's extensive standard library covers many programming needs, +there often comes a time when you need to add 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 was 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. However, not all +problems were solved; end-users had to rely on ``easy_install`` or +``pip`` to download third-party modules from PyPI, uninstall distributions or do +other maintenance operations. Packaging is a more complete replacement for +Distutils, in the standard library, with a backport named Distutils2 available +for older Python versions. + +This document is aimed primarily at 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 +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:`packaging-index` manual. + + +.. _packaging-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 can be installed just like any other software on your platform. For example, +the module's 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 and derivative +systems, and so forth. + +In that case, you would use the standard system tools to download and install +the specific installer for your platform and its dependencies. + +Of course, things will not always be that easy. You might be interested in a +module whose distribution 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 addresses the building and installing +of modules from standard source distributions. + + +.. _packaging-distutils: + +The Python standard: Distutils +------------------------------ + +If you download a source distribution of a module, it will be obvious whether +it was packaged and distributed using 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 may contain a +:file:`setup.cfg` file and a file named :file:`README.txt` ---or possibly just +:file:`README`--- explaining that building and installing the module +distribution is a simple matter of issuing the following command at your shell's +prompt:: + + python setup.py install + +Third-party projects have extended Distutils to work around its limitations or +add functionality. After some years of near-inactivity in Distutils, a new +maintainer has started to standardize good ideas in PEPs and implement them in a +new, improved version of Distutils, called Distutils2 or Packaging. + + +.. _packaging-new-standard: + +The new standard: Packaging +--------------------------- + +The rules described in the first paragraph above apply to Packaging-based +projects too: a source distribution will have a name like +:file:`widget-0.9.7.zip`. One of the main differences with Distutils is that +distributions no longer have a :file:`setup.py` script; it used to cause a +number of issues. Now there is a unique script installed with Python itself:: + + pysetup install widget-0.9.7.zip + +Running this command is enough to build and install projects (Python modules or +packages, scripts or whole applications), without even having to unpack the +archive. It is also compatible with Distutils-based distributions. + +Unless you have to perform non-standard installations or customize the build +process, you can stop reading this manual ---the above command is everything you +need to get out of it. + +With :program:`pysetup`, you won't even have to manually download a distribution +before installing it; see :ref:`packaging-pysetup`. + + +.. _packaging-standard-install: + +Standard build and install +========================== + +As described in section :ref:`packaging-new-standard`, building and installing +a module distribution using Packaging usually comes down to one simple +command:: + + pysetup run install_dist + +This is a command that should be run in a terminal. On Windows, it is called a +command prompt and found in :menuselection:`Start --> Accessories`; Powershell +is a popular alternative. + + +.. _packaging-platform-variations: + +Platform variations +------------------- + +The setup command is meant to be run from the root directory of the source +distribution, 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 +steps to follow are these:: + + gunzip -c foo-1.0.tar.gz | tar xf - # unpacks into directory foo-1.0 + cd foo-1.0 + pysetup run install_dist + +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`. To actually unpack the archive, you can use either +an archive manipulator with a graphical user interface (such as WinZip or 7-Zip) +or a command-line tool (such as :program:`unzip`, :program:`pkunzip` or, again, +:program:`7z`). Then, open a command prompt window and run:: + + cd c:\Temp\foo-1.0 + pysetup run install_dist + + +.. _packaging-splitting-up: + +Splitting the job up +-------------------- + +Running ``pysetup run install_dist`` builds and installs all modules in one go. 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 a valuable tool when different users will perform +separately the build and install steps. For example, you might want to build a +module distribution and hand it off to a system administrator for installation +(or do it yourself, but with super-user or admin privileges). + +For example, to build everything in one step and then install everything +in a second step, you aptly invoke two distinct Packaging commands:: + + pysetup run build + pysetup run install_dist + +If you do this, you will notice that invoking the :command:`install_dist` command +first runs the :command:`build` command, which ---in this case--- quickly +notices it can spare itself the work, since everything in the :file:`build` +directory is up-to-date. + +You may often ignore this ability to divide the process in steps if all you do +is installing modules downloaded from the Internet, but it's very handy for +more advanced tasks. If you find yourself in the need for distributing your own +Python modules and extensions, though, you'll most likely run many individual +Packaging commands. + + +.. _packaging-how-build-works: + +How building works +------------------ + +As implied above, the :command:`build` command is responsible for collecting +and placing the files to be installed 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 specify +a different build directory with the :option:`--build-base` option. For example:: + + pysetup run build --build-base /tmp/pybuild/foo-1.0 + +(Or you could do this permanently with a directive in your system or personal +Packaging configuration file; see section :ref:`packaging-config-files`.) +In the usual case, however, all this is unnecessary. + +The build tree's default layout looks like so:: + + --- 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 (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 during the compile/link process which are not intended +to be installed. In either case, the :file:`lib` (or :file:`lib.{plat}`) directory +contains all Python modules (pure Python and extensions) to be installed. + +In the future, more directories will be added to handle Python scripts, +documentation, binary executables, and whatever else is required to install +Python modules and applications. + + +.. _packaging-how-install-works: + +How installation works +---------------------- + +After the :command:`build` command is run (whether explicitly or by the +:command:`install_dist` command on your behalf), the work of the :command:`install_dist` +command is relatively simple: all it has to do is copy the contents of +:file:`build/lib` (or :file:`build/lib.{plat}`) to the installation directory +of your choice. + +If you don't choose an installation directory ---i.e., if you just run +``pysetup run install_dist``\ --- then the :command:`install_dist` command +installs to the standard location for third-party Python modules. This location +varies by platform and depending on 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}\\Lib\\site-packages` | :file:`C:\\Python{XY}\\Lib\\site-packages` | \(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. + +.. TODO link to Doc/using instead of duplicating + +To start the interactive Python interpreter, you need to follow a slightly +different recipe for each platform. Under Unix, just type :command:`python` at +the shell prompt. Under Windows (assuming the Python executable is on your +:envvar:`PATH`, which is the usual case), you can choose :menuselection:`Start --> Run`, +type ``python`` and press ``enter``. Alternatively, you can simply execute +:command:`python` at a command prompt (:menuselection:`Start --> Accessories`) +or in Powershell. + +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 3.3 (r32:88445, Apr 2 2011, 10:43:54) + Type "help", "copyright", "credits" or "license" for more information. + >>> import sys + >>> sys.prefix + '/usr' + >>> sys.exec_prefix + '/usr' + +A few other placeholders are used in this document: :file:`{X.Y}` stands for the +version of Python, for example ``3.2``; :file:`{abiflags}` will be replaced by +the value of :data:`sys.abiflags` or the empty string for platforms which don't +define ABI flags; :file:`{distname}` will be replaced by the name of the module +distribution being installed. Dots and capitalization are important in the +paths; for example, a value that uses ``python3.2`` on UNIX will typically use +``Python32`` on Windows. + +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:`packaging-alt-install`. If you want to customize your +installation directories more heavily, see section :ref:`packaging-custom-install`. + + +.. _packaging-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 Packaging :command:`install_dist` 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_dist` 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. + +Note that the various alternate installation schemes are mutually exclusive: you +can pass ``--user``, or ``--home``, or ``--prefix`` and ``--exec-prefix``, or +``--install-base`` and ``--install-platbase``, but you can't mix from these +groups. + + +.. _packaging-alt-install-user: + +Alternate installation: the user scheme +--------------------------------------- + +This scheme is designed to be the most convenient solution for users that don't +have write permission to the global site-packages directory or don't want to +install into it. It is enabled with a simple option:: + + pysetup run install_dist --user + +Files will be installed into subdirectories of :data:`site.USER_BASE` (written +as :file:`{userbase}` hereafter). This scheme installs pure Python modules and +extension modules in the same location (also known as :data:`site.USER_SITE`). +Here are the values for UNIX, including non-framework builds on Mac OS X: + +=============== =========================================================== +Type of file Installation directory +=============== =========================================================== +modules :file:`{userbase}/lib/python{X.Y}/site-packages` +scripts :file:`{userbase}/bin` +data :file:`{userbase}` +C headers :file:`{userbase}/include/python{X.Y}` +=============== =========================================================== + +Framework builds on Mac OS X use these paths: + +=============== =========================================================== +Type of file Installation directory +=============== =========================================================== +modules :file:`{userbase}/lib/python/site-packages` +scripts :file:`{userbase}/bin` +data :file:`{userbase}` +C headers :file:`{userbase}/include/python` +=============== =========================================================== + +And here are the values used on Windows: + +=============== =========================================================== +Type of file Installation directory +=============== =========================================================== +modules :file:`{userbase}\\Python{XY}\\site-packages` +scripts :file:`{userbase}\\Scripts` +data :file:`{userbase}` +C headers :file:`{userbase}\\Python{XY}\\Include` +=============== =========================================================== + +The advantage of using this scheme compared to the other ones described below is +that the user site-packages directory is under normal conditions always included +in :data:`sys.path` (see :mod:`site` for more information), which means that +there is no additional step to perform after running ``pysetup`` to finalize the +installation. + +The :command:`build_ext` command also has a ``--user`` option to add +:file:`{userbase}/include` to the compiler search path for header files and +:file:`{userbase}/lib` to the compiler search path for libraries as well as to +the runtime search path for shared C libraries (rpath). + + +.. _packaging-alt-install-home: + +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 concept 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/`. +In spite of its name's origin, this scheme can be used by anyone, regardless +of the operating system. + +Installing a new module distribution in this way is as simple as :: + + pysetup run install_dist --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_dist` command +will expand this to your home directory:: + + pysetup run install_dist --home ~ + +To make Python find the distributions installed with this scheme, you may have +to :ref:`modify Python's search path <inst-search-path>` or edit +:mod:`sitecustomize` (see :mod:`site`) to call :func:`site.addsitedir` or edit +:data:`sys.path`. + +The :option:`--home` option defines the base directory for the installation. +Under it, files are installed to the following directories: + +=============== =========================================================== +Type of file Installation directory +=============== =========================================================== +modules :file:`{home}/lib/python` +scripts :file:`{home}/bin` +data :file:`{home}` +C headers :file:`{home}/include/python` +=============== =========================================================== + +(Mentally replace slashes with backslashes if you're on Windows.) + + +.. _packaging-alt-install-prefix-unix: + +Alternate installation: Unix (the prefix scheme) +------------------------------------------------ + +The "prefix scheme" is useful when you wish to use one Python installation to +run the build command, 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 +user and home schemes come before. 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 :: + + pysetup run install_dist --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 :: + + pysetup run install_dist --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 +================= ========================================================== +Python modules :file:`{prefix}/lib/python{X.Y}/site-packages` +extension modules :file:`{exec-prefix}/lib/python{X.Y}/site-packages` +scripts :file:`{prefix}/bin` +data :file:`{prefix}` +C headers :file:`{prefix}/include/python{X.Y}{abiflags}` +================= ========================================================== + +.. XXX misses an entry for platinclude + +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 ``pysetup run install_dist`` without any other +options, you're using it. + +Note that installing extensions to an alternate Python installation doesn't have +anything to do with how those extensions are built: in particular, extensions +will be compiled using the Python header files (:file:`Python.h` and friends) +installed with the Python interpreter used to run the build command. It is +therefore your responsibility to ensure compatibility between the interpreter +intended to run extensions installed in this way and the interpreter used to +build these same extensions. To avoid problems, it is best to make sure 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.) + + +.. _packaging-alt-install-prefix-windows: + +Alternate installation: Windows (the prefix scheme) +--------------------------------------------------- + +Windows has a different and vaguer notion of home directories than Unix, and +since its standard Python installation is simpler, the :option:`--prefix` option +has traditionally been used to install additional packages to arbitrary +locations. :: + + pysetup run install_dist --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, which means that +pure Python modules and extension modules are installed into the same location. +Files are installed as follows: + +=============== ========================================================== +Type of file Installation directory +=============== ========================================================== +modules :file:`{prefix}\\Lib\\site-packages` +scripts :file:`{prefix}\\Scripts` +data :file:`{prefix}` +C headers :file:`{prefix}\\Include` +=============== ========================================================== + + +.. _packaging-custom-install: + +Custom installation +=================== + +Sometimes, the alternate installation schemes described in section +:ref:`packaging-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*. + +To create a custom installation scheme, you start with one of the alternate +schemes and override some of the installation directories used for the various +types of files, using these options: + +====================== ======================= +Type of file Override option +====================== ======================= +Python modules ``--install-purelib`` +extension modules ``--install-platlib`` +all modules ``--install-lib`` +scripts ``--install-scripts`` +data ``--install-data`` +C headers ``--install-headers`` +====================== ======================= + +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 +``--prefix`` and ``--exec-prefix`` options; using ``--install-lib`` will +override values computed or given for ``--install-purelib`` and +``--install-platlib``, and is recommended for schemes that don't make a +difference between Python and extension modules.) + +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 and, in this case, it makes most sense to supply +a relative path, which will be interpreted relative to the installation base +directory (in our example, your home directory):: + + pysetup run install_dist --home ~ --install-scripts scripts + +Another Unix example: suppose your Python installation was built and installed +with a prefix of :file:`/usr/local/python`. Thus, in 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:: + + pysetup run install_dist --install-scripts /usr/local/bin + +This command performs an installation using the "prefix scheme", where the +prefix is whatever your Python interpreter was installed with ---in this case, +:file:`/usr/local/python`. + +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, +Python and extension modules, which can conveniently be both controlled by one +option:: + + pysetup run install_dist --install-lib Site + +.. XXX Nothing is installed right under prefix in windows, is it?? + +The specified installation directory is relative to :file:`{prefix}`. Of +course, you also have to ensure that this directory is in Python's module +search path, such as by putting a :file:`.pth` file in a site directory (see +:mod:`site`). See section :ref:`packaging-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. Using relative paths is recommended here. +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:: + + pysetup run install_dist --home ~ \ + --install-purelib python/lib \ + --install-platlib python/'lib.$PLAT' \ + --install-scripts python/scripts \ + --install-data python/data + +or, equivalently, :: + + pysetup run install_dist --home ~/python \ + --install-purelib lib \ + --install-platlib 'lib.$PLAT' \ + --install-scripts scripts \ + --install-data data + +``$PLAT`` doesn't need to be defined as an environment variable ---it will also +be expanded by Packaging as it parses your command line options, just as it +does when parsing your configuration file(s). (More on that later.) + +Obviously, specifying the entire installation scheme every time you install a +new module distribution would be very tedious. To spare you all that work, you +can store it in a Packaging configuration file instead (see section +:ref:`packaging-config-files`), like so:: + + [install_dist] + install-base = $HOME + install-purelib = python/lib + install-platlib = python/lib.$PLAT + install-scripts = python/scripts + install-data = python/data + +or, equivalently, :: + + [install_dist] + 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 override their installation +base directory when running the setup script. For example, :: + + pysetup run install_dist --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'd probably +want to supply an installation base of :file:`/tmp/python`.) + +You may have noticed the use of ``$HOME`` and ``$PLAT`` in the sample +configuration file. These are Packaging configuration variables, which +bear a strong resemblance to environment variables. In fact, you can use +environment variables in configuration files on platforms that have such a notion, but +Packaging additionally defines a few extra variables that may not be in your +environment, such as ``$PLAT``. Of course, on systems that don't have +environment variables, such as Mac OS 9, the configuration variables supplied by +the Packaging are the only ones you can use. See section :ref:`packaging-config-files` +for details. + +.. XXX which vars win out eventually in case of clash env or Packaging? + +.. XXX need some Windows examples---when would custom installation schemes be + needed on those platforms? + + +.. XXX Move this section to Doc/using + +.. _packaging-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 this path is configured into the Python binary when the interpreter is built. +You can obtain the search 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. + +The expected convention for locally installed packages is to put them in the +:file:`{...}/site-packages/` directory, but you may want to choose a different +location for some reason. For example, if your site kept by convention all web +server-related software under :file:`/www`. Add-on Python modules might then +belong in :file:`/www/python`, and in order to import them, this directory would +have to be added to ``sys.path``. There are several ways to solve this problem. + +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. See the documentation of +the :mod:`site` module 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 3.3 to 3.3.1, 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. + +Alternatively, 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 non-existent paths.) + +Finally, ``sys.path`` is just a regular Python list, so any Python application +can modify it by adding or removing entries. + + +.. _packaging-config-files: + +Configuration files for Packaging +================================= + +As mentioned above, you can use configuration files to store personal or site +preferences for any option supported by any Packaging command. Depending on your +platform, you can use one of two or three possible configuration files. These +files will be read before parsing the command-line, so they take precedence over +default values. In turn, the command-line will override configuration files. +Lastly, if there are multiple configuration files, values from files read +earlier will be overridden by values from files read later. + +.. XXX "one of two or three possible..." seems wrong info. Below always 3 files + are indicated in the tables. + + +.. _packaging-config-filenames: + +Location and names of configuration files +----------------------------------------- + +The name and location of the configuration files vary slightly across +platforms. On Unix and Mac OS X, these are the three configuration files listed +in the order they are processed: + ++--------------+----------------------------------------------------------+-------+ +| Type of file | Location and filename | Notes | ++==============+==========================================================+=======+ +| system | :file:`{prefix}/lib/python{ver}/packaging/packaging.cfg` | \(1) | ++--------------+----------------------------------------------------------+-------+ +| personal | :file:`$HOME/.pydistutils.cfg` | \(2) | ++--------------+----------------------------------------------------------+-------+ +| local | :file:`setup.cfg` | \(3) | ++--------------+----------------------------------------------------------+-------+ + +Similarly, the configuration files on Windows ---also listed in the order they +are processed--- are these: + ++--------------+-------------------------------------------------+-------+ +| Type of file | Location and filename | Notes | ++==============+=================================================+=======+ +| system | :file:`{prefix}\\Lib\\packaging\\packaging.cfg` | \(4) | ++--------------+-------------------------------------------------+-------+ +| personal | :file:`%HOME%\\pydistutils.cfg` | \(5) | ++--------------+-------------------------------------------------+-------+ +| local | :file:`setup.cfg` | \(3) | ++--------------+-------------------------------------------------+-------+ + +On all platforms, the *personal* file can be temporarily disabled by +means of the `--no-user-cfg` option. + +Notes: + +(1) + Strictly speaking, the system-wide configuration file lives in the directory + where Packaging is installed. + +(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. Packaging uses the + :func:`os.path.expanduser` function to do this. + +(3) + I.e., in the current directory (usually the location of the setup script). + +(4) + (See also note (1).) Python's default installation prefix is + :file:`C:\\Python`, so the system configuration file is normally + :file:`C:\\Python\\Lib\\packaging\\packaging.cfg`. + +(5) + On Windows, if the :envvar:`HOME` environment variable is not defined, + :envvar:`USERPROFILE` then :envvar:`HOMEDRIVE` and :envvar:`HOMEPATH` will + be tried. Packaging uses the :func:`os.path.expanduser` function to do this. + + +.. _packaging-config-syntax: + +Syntax of configuration files +----------------------------- + +All Packaging configuration files share the same syntax. Options defined in +them are grouped into sections, and each Packaging command gets its own section. +Additionally, there's a ``global`` section for options that affect every command. +Sections consist of one or more lines containing a single option specified as +``option = value``. + +For example, here's a complete configuration file that forces all commands to +run quietly by default:: + + [global] + verbose = 0 + +If this was the system configuration file, it would affect all processing +of any Python module distribution by any user on the current system. If it was +installed as your personal configuration file (on systems that support them), +it would affect only module distributions processed by you. Lastly, if it was +used as the :file:`setup.cfg` for a particular module distribution, it would +affect that distribution only. + +.. XXX "(on systems that support them)" seems wrong info + +If you wanted to, 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:: + + pysetup run 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 configuration files +has no such implication; it only means that if the command is run, the options +for it in the configuration file will apply. (This is also true if you run +other commands that derive values from it.) + +You can find out the complete list of options for any command using the +:option:`--help` option, e.g.:: + + pysetup run build --help + +and you can find out the complete list of global options by using +:option:`--help` without a command:: + + pysetup run --help + +See also the "Reference" section of the "Distributing Python Modules" manual. + +.. XXX no links to the relevant section exist. + + +.. _packaging-building-ext: + +Building extensions: tips and tricks +==================================== + +Whenever possible, Packaging tries to use the configuration information made +available by the Python interpreter used to run `pysetup`. +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 Packaging behaviour. + + +.. _packaging-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. + +.. TODO update to new setup.cfg + +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 ``pysetup run 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. + + +.. _packaging-non-ms-compilers: + +Using non-Microsoft compilers on Windows +---------------------------------------- + +.. sectionauthor:: Rene Liebscher <R.Liebscher@gmx.de> + + + +Borland/CodeGear C++ +^^^^^^^^^^^^^^^^^^^^ + +This subsection describes the necessary steps to use Packaging 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 Packaging manage to use these libraries with their changed names? If +the extension needs a library (eg. :file:`foo`) Packaging 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 Packaging compile your extension with Borland, C++ you now have to +type:: + + pysetup run 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 Packaging (see +section :ref:`packaging-config-files`.) + + +.. seealso:: + + `C++Builder Compiler <http://www.codegear.com/downloads/free/cppbuilder>`_ + 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 +^^^^^^^^^^^^^^^^^^^^^^ + +This section describes the necessary steps to use Packaging 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. + +Not all extensions can be built with MinGW or Cygwin, but many can. Extensions +most likely to not work are those that use C++ or depend on Microsoft Visual C +extensions. + +To let Packaging compile your extension with Cygwin, you have to type:: + + pysetup run build --compiler=cygwin + +and for Cygwin in no-cygwin mode [#]_ or for MinGW, type:: + + pysetup run build --compiler=mingw32 + +If you want to use any of these options/compilers as default, you should +consider writing it in your personal or system-wide configuration file for +Packaging (see section :ref:`packaging-config-files`.) + +Older Versions of Python and MinGW +"""""""""""""""""""""""""""""""""" +The following instructions only apply if you're using a version of Python +inferior to 2.4.1 with a MinGW inferior to 3.0.0 (with +:file:`binutils-2.13.90-20030111-1`). + +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://www.emmestech.com/software/pexports-0.43/download_pexports.html). + +.. 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. + + +.. 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. + + +.. 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`. |