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88 lines
3.3 KiB
TeX
88 lines
3.3 KiB
TeX
\section{\module{site} ---
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Site-specific configuration hook}
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\declaremodule{standard}{site}
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\modulesynopsis{A standard way to reference site-specific modules.}
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\strong{This module is automatically imported during initialization.}
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In earlier versions of Python (up to and including 1.5a3), scripts or
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modules that needed to use site-specific modules would place
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\samp{import site} somewhere near the top of their code. This is no
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longer necessary.
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This will append site-specific paths to the module search path.
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\indexiii{module}{search}{path}
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It starts by constructing up to four directories from a head and a
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tail part. For the head part, it uses \code{sys.prefix} and
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\code{sys.exec_prefix}; empty heads are skipped. For
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the tail part, it uses the empty string (on Macintosh or Windows) or
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it uses first \file{lib/python\shortversion/site-packages} and then
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\file{lib/site-python} (on \UNIX{}). For each of the distinct
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head-tail combinations, it sees if it refers to an existing directory,
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and if so, adds to \code{sys.path}, and also inspects the path for
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configuration files.
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\indexii{site-python}{directory}
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\indexii{site-packages}{directory}
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A path configuration file is a file whose name has the form
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\file{\var{package}.pth}; its contents are additional items (one
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per line) to be added to \code{sys.path}. Non-existing items are
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never added to \code{sys.path}, but no check is made that the item
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refers to a directory (rather than a file). No item is added to
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\code{sys.path} more than once. Blank lines and lines beginning with
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\code{\#} are skipped.
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\index{package}
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\indexiii{path}{configuration}{file}
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For example, suppose \code{sys.prefix} and \code{sys.exec_prefix} are
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set to \file{/usr/local}. The Python \version\ library is then
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installed in \file{/usr/local/lib/python\shortversion} (where only the
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first three characters of \code{sys.version} are used to form the
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installation path name). Suppose this has a subdirectory
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\file{/usr/local/lib/python\shortversion/site-packages} with three
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subsubdirectories, \file{foo}, \file{bar} and \file{spam}, and two
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path configuration files, \file{foo.pth} and \file{bar.pth}. Assume
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\file{foo.pth} contains the following:
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\begin{verbatim}
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# foo package configuration
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foo
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bar
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bletch
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\end{verbatim}
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and \file{bar.pth} contains:
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\begin{verbatim}
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# bar package configuration
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bar
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\end{verbatim}
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Then the following directories are added to \code{sys.path}, in this
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order:
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\begin{verbatim}
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/usr/local/lib/python1.5/site-packages/bar
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/usr/local/lib/python1.5/site-packages/foo
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\end{verbatim}
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Note that \file{bletch} is omitted because it doesn't exist; the
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\file{bar} directory precedes the \file{foo} directory because
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\file{bar.pth} comes alphabetically before \file{foo.pth}; and
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\file{spam} is omitted because it is not mentioned in either path
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configuration file.
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After these path manipulations, an attempt is made to import a module
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named \module{sitecustomize}\refmodindex{sitecustomize}, which can
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perform arbitrary site-specific customizations. If this import fails
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with an \exception{ImportError} exception, it is silently ignored.
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Note that for some non-\UNIX{} systems, \code{sys.prefix} and
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\code{sys.exec_prefix} are empty, and the path manipulations are
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skipped; however the import of
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\module{sitecustomize}\refmodindex{sitecustomize} is still attempted.
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