Setting Up Cygwin. Cygwin uses packages to manage installing various software. When the default Install from Internet option is chosen.

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 manual. May also be of interest. 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 anyway). 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. 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. Foo-1.0.tar.gz or widget-0.9.7.zip. Next, the archive will unpack into a similarly-named directory: foo-1.0 or widget-0.9.7. Additionally, the distribution will contain a setup script setup.py, and a file named README.txt or possibly just README, which should explain that building and installing the module distribution is a simple matter of running one command from a terminal. 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 install command first runs the build command, which—in this case—quickly notices that it has nothing to do, since everything in the 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. Build/ --- lib/ or --- build/ --- lib./ temp./ where expands to a brief description of the current OS/hardware platform and Python version. The first form, with just a 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 directories, is used.

In that case, the temp. Ford Focus Fuel Pump Driver Module Problems. Plat directory holds temporary files generated by the compile/link process that don’t actually get installed. In either case, the lib (or 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. How installation works After the build command runs (whether you run it explicitly, or the install command does it for you), the work of the install command is relatively simple: all it has to do is copy everything under build/lib (or 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 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. 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' A few other placeholders are used in this document: X.Y stands for the version of Python, for example 2.7; 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 python2.7 on UNIX will typically use Python27 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. If you want to customize your installation directories more heavily, see section on custom installations. 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 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 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. 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.

Python setup.py install --user Files will be installed into subdirectories of (written as userbase hereafter). This scheme installs pure Python modules and extension modules in the same location (also known as ). Python setup.py install --home=~ To make Python find the distributions installed with this scheme, you may have to or edit sitecustomize (see ) to call or edit.

The --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 modules home /lib/python scripts home /bin data home C headers home /include/python/ distname (Mentally replace slashes with backslashes if you’re on Windows.). 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. James Joyce Ulise Romana Pdf Free. , 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 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 /usr, rather than the more traditional /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 /usr/local/lib/python2. X rather than /usr/lib/python2.

This can be done with. /usr/local/bin/python setup.py install --prefix=/mnt/@server/export In either case, the --prefix option defines the installation base, and the --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 --exec-prefix is not supplied, it defaults to --prefix. Files are installed as follows: Type of file Installation directory Python modules prefix /lib/python X.Y /site-packages extension modules exec-prefix /lib/python X.Y /site-packages scripts prefix /bin data prefix C headers prefix /include/python X.Y / distname There is no requirement that --prefix or --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 --prefix and --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 ( 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 --prefix and --exec-prefix don’t even point to an alternate Python installation, this is immaterial.). Python setup.py install --prefix=' Temp Python' to install modules to the Temp Python directory on the current drive.

The installation base is defined by the --prefix option; the --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 prefix Lib site-packages scripts prefix Scripts data prefix C headers prefix Include distname. Custom Installation Sometimes, the alternate installation schemes described in section 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 ~/scripts rather than ~/bin. As you might expect, you can override this directory with the --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 --install-scripts=/usr/local/bin (This performs an installation using the “prefix scheme,” where the prefix is whatever your Python interpreter was installed with— /usr/local/python in this case.) If you maintain Python on Windows, you might want third-party modules to live in a subdirectory of prefix, rather than right in 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. Python setup.py install --install-lib=Site The specified installation directory is relative to prefix.

Of course, you also have to ensure that this directory is in Python’s module search path, such as by putting a.pth file in a site directory (see ). See section 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 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=~/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). 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 ).

Python setup.py install --install-base=/tmp would install pure modules to /tmp/python/lib in the first case, and to /tmp/lib in the second case. (For the second case, you probably want to supply an installation base of /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 for details. $ python Python 2.2 (#11, Oct 3 2002, 13:31:27) [GCC 2.1 (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 /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 /www.

Add-on Python modules might then belong in /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./site-packages/ directory. Path configuration files have an extension of.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.pth file. See the documentation of the module for more information.

A slightly less convenient way is to edit the site.py file in Python’s standard library, and modify sys.path. Site.py is automatically imported when the Python interpreter is executed, unless the switch is supplied to suppress this behaviour. So you could simply edit 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) 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. Sets an alternate value for the prefix of the Python installation. For example, if 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 variable can be set to a list of paths that will be added to the beginning of sys.path.

For example, if 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 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. 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. 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 prefix /lib/python ver /distutils/distutils.cfg (1) personal $HOME/.pydistutils.cfg (2) local setup.cfg (3) And on Windows, the configuration files are: Type of file Location and filename Notes system prefix Lib distutils distutils.cfg (4) personal%HOME% pydistutils.cfg (5) local setup.cfg (3) On all platforms, the “personal” file can be temporarily disabled by passing the –no-user-cfg option. Notes: • 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 prefix /lib/python1.5/site-packages/distutils, so the system configuration file should be put there under Python 1.5.2.

• On Unix, if the HOME environment variable is not defined, the user’s home directory will be determined with the getpwuid() function from the standard module. This is done by the function used by Distutils. • I.e., in the current directory (usually the location of the setup script).

• (See also note (1).) Under Python 1.6 and later, Python’s default “installation prefix” is C: Python, so the system configuration file is normally C: Python Lib distutils distutils.cfg. Under Python 1.5.2, the default prefix was C: Program Files Python, and the Distutils were not part of the standard library—so the system configuration file would be C: Program Files Python distutils distutils.cfg in a standard Python 1.5.2 installation under Windows. • On Windows, if the HOME environment variable is not defined, USERPROFILE then HOMEDRIVE and HOMEPATH will be tried.

This is done by the function used by Distutils. [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 setup.cfg for a particular module distribution, it affects only that distribution. You could override the default “build base” directory and make the build* commands always forcibly rebuild all files with the following.

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 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 Setup file, if present, is parsed in order to get a list of extensions to build. Each line in a Setup describes a single module.

Lines have the following structure. [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.c are assumed to be written in C, filenames ending in.C,.cc, and.c++ are assumed to be C++, and filenames ending in.m or.mm are assumed to be in Objective C. • cpparg is an argument for the C preprocessor, and is anything starting with -I, -D, -U or -C. • library is anything ending in.a or beginning with -l or -L. If a particular platform requires a special library on your platform, you can add it by editing the Setup file and running python setup.py build. For example, if the module defined by the line.

Foo foomodule.c -Xcompiler -o32 -Xlinker -shared -lm The next option after -Xcompiler and -Xlinker will be appended to the proper command line, so in the above example the compiler will be passed the -o32 option, and the linker will be passed -shared. If a compiler option requires an argument, you’ll have to supply multiple -Xcompiler options; for example, to pass -x c++ the Setup file would have to contain -Xcompiler -x -Xcompiler c++. Compiler flags can also be supplied through setting the CFLAGS environment variable. If set, the contents of CFLAGS will be added to the compiler flags specified in the Setup file. Borland/CodeGear 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 python25.lib into the Borland format. You can do this as follows. Coff2omf python25.lib python25_bcpp.lib The coff2omf program comes with the Borland compiler. The file python25.lib is in the 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. Foo) Distutils checks first if it finds a library with suffix _bcpp (eg. Foo_bcpp.lib) and then uses this library. In the case it doesn’t find such a special library it uses the default name ( foo.lib.) To let Distutils compile your extension with Borland C++ you now have to type. GNU C / Cygwin / MinGW 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. 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 Distutils compile your extension with Cygwin you have to type.