mirror of https://github.com/python/cpython
85 lines
3.2 KiB
ReStructuredText
85 lines
3.2 KiB
ReStructuredText
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:mod:`site` --- Site-specific configuration hook
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================================================
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.. module:: site
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:synopsis: A standard way to reference site-specific modules.
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**This module is automatically imported during initialization.** The automatic
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import can be suppressed using the interpreter's :option:`-S` option.
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.. index:: triple: module; search; path
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Importing this module will append site-specific paths to the module search path.
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.. index::
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pair: site-python; directory
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pair: site-packages; directory
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It starts by constructing up to four directories from a head and a tail part.
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For the head part, it uses ``sys.prefix`` and ``sys.exec_prefix``; empty heads
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are skipped. For the tail part, it uses the empty string and then
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:file:`lib/site-packages` (on Windows) or
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:file:`lib/python|version|/site-packages` and then :file:`lib/site-python` (on
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Unix and Macintosh). For each of the distinct head-tail combinations, it sees
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if it refers to an existing directory, and if so, adds it to ``sys.path`` and
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also inspects the newly added path for configuration files.
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A path configuration file is a file whose name has the form :file:`package.pth`
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and exists in one of the four directories mentioned above; its contents are
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additional items (one per line) to be added to ``sys.path``. Non-existing items
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are never added to ``sys.path``, but no check is made that the item refers to a
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directory (rather than a file). No item is added to ``sys.path`` more than
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once. Blank lines and lines beginning with ``#`` are skipped. Lines starting
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with ``import`` (followed by space or tab) are executed.
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.. index::
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single: package
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triple: path; configuration; file
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For example, suppose ``sys.prefix`` and ``sys.exec_prefix`` are set to
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:file:`/usr/local`. The Python X.Y library is then installed in
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:file:`/usr/local/lib/python{X.Y}` (where only the first three characters of
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``sys.version`` are used to form the installation path name). Suppose this has
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a subdirectory :file:`/usr/local/lib/python{X.Y}/site-packages` with three
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subsubdirectories, :file:`foo`, :file:`bar` and :file:`spam`, and two path
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configuration files, :file:`foo.pth` and :file:`bar.pth`. Assume
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:file:`foo.pth` contains the following::
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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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and :file:`bar.pth` contains::
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# bar package configuration
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bar
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Then the following directories are added to ``sys.path``, in this order::
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/usr/local/lib/python2.3/site-packages/bar
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/usr/local/lib/python2.3/site-packages/foo
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Note that :file:`bletch` is omitted because it doesn't exist; the :file:`bar`
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directory precedes the :file:`foo` directory because :file:`bar.pth` comes
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alphabetically before :file:`foo.pth`; and :file:`spam` is omitted because it is
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not mentioned in either path configuration file.
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.. index:: module: sitecustomize
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After these path manipulations, an attempt is made to import a module named
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:mod:`sitecustomize`, which can perform arbitrary site-specific customizations.
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If this import fails with an :exc:`ImportError` exception, it is silently
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ignored.
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.. index:: module: sitecustomize
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Note that for some non-Unix systems, ``sys.prefix`` and ``sys.exec_prefix`` are
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empty, and the path manipulations are skipped; however the import of
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:mod:`sitecustomize` is still attempted.
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