5. Creating Built Distributions

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5. Creating Built Distributions

A ``built distribution'' is what you're probably used to thinking of either as a ``binary package'' or an ``installer'' (depending on your background). It's not necessarily binary, though, because it might contain only Python source code and/or byte-code; and we don't call it a package, because that word is already spoken for in Python. (And ``installer'' is a term specific to the world of mainstream desktop systems.)

A built distribution is how you make life as easy as possible for installers of your module distribution: for users of RPM-based Linux systems, it's a binary RPM; for Windows users, it's an executable installer; for Debian-based Linux users, it's a Debian package; and so forth. Obviously, no one person will be able to create built distributions for every platform under the sun, so the Distutils are designed to enable module developers to concentrate on their specialty--writing code and creating source distributions--while an intermediary species called packagers springs up to turn source distributions into built distributions for as many platforms as there are packagers.

Of course, the module developer could be his own packager; or the packager could be a volunteer ``out there'' somewhere who has access to a platform which the original developer does not; or it could be software periodically grabbing new source distributions and turning them into built distributions for as many platforms as the software has access to. Regardless of who they are, a packager uses the setup script and the `bdist` command family to generate built distributions.

As a simple example, if I run the following command in the Distutils source tree:

    python setup.py bdist

then the Distutils builds my module distribution (the Distutils itself in this case), does a ``fake'' installation (also in the build directory), and creates the default type of built distribution for my platform. The default format for built distributions is a ``dumb'' tar file on Unix, and a simple executable installer on Windows. (That tar file is considered ``dumb'' because it has to be unpacked in a specific location to work.)

Thus, the above command on a Unix system creates Distutils-1.0.plat.tar.gz; unpacking this tarball from the right place installs the Distutils just as though you had downloaded the source distribution and run `python setup.py install`. (The ``right place'' is either the root of the filesystem or Python's prefix directory, depending on the options given to the `bdist_dumb` command; the default is to make dumb distributions relative to prefix.)

Obviously, for pure Python distributions, this isn't any simpler than just running `python setup.py install`--but for non-pure distributions, which include extensions that would need to be compiled, it can mean the difference between someone being able to use your extensions or not. And creating ``smart'' built distributions, such as an RPM package or an executable installer for Windows, is far more convenient for users even if your distribution doesn't include any extensions.

The `bdist` command has a --formats option, similar to the `sdist` command, which you can use to select the types of built distribution to generate: for example,

    python setup.py bdist --format=zip

would, when run on a Unix system, create Distutils-1.0.plat.zip--again, this archive would be unpacked from the root directory to install the Distutils.

The available formats for built distributions are:

Format | Description | Notes
--- | --- | ---
`gztar` | gzipped tar file (.tar.gz) | (1),(3)
`ztar` | compressed tar file (.tar.Z) | (3)
`tar` | tar file (.tar) | (3)
`zip` | zip file (.zip) | (4)
`rpm` | RPM | (5)
`pkgtool` | Solaris pkgtool |
`sdux` | HP-UX swinstall |
`rpm` | RPM | (5)
`wininst` | self-extracting ZIP file for Windows | (2),(4)

Notes:

(1)
  default on Unix
(2)
  default on Windows to-do!
(3)
  requires external utilities: tar and possibly one of gzip, bzip2, or compress
(4)
  requires either external zip utility or `zipfile` module (part of the standard Python library since Python 1.6)
(5)
  requires external rpm utility, version 3.0.4 or better (use `rpm --version` to find out which version you have)

You don't have to use the `bdist` command with the --formats option; you can also use the command that directly implements the format you're interested in. Some of these `bdist` ``sub-commands'' actually generate several similar formats; for instance, the `bdist_dumb` command generates all the ``dumb'' archive formats (`tar`, `ztar`, `gztar`, and `zip`), and `bdist_rpm` generates both binary and source RPMs. The `bdist` sub-commands, and the formats generated by each, are:

Command | Formats
--- | ---
`bdist_dumb` | tar, ztar, gztar, zip
`bdist_rpm` | rpm, srpm
`bdist_wininst` | wininst

The following sections give details on the individual `bdist_*` commands.