Original Translation
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Alternate installation: Unix (the prefix scheme)
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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.
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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 ::
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/usr/bin/python setup.py install --prefix=/usr/local
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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 ::
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/usr/local/bin/python setup.py install --prefix=/mnt/@server/export
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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:
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:file:`{prefix}/bin`
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:file:`{prefix}/share`
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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.