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# 27.12. `site` — Site-specific configuration hook

This module is automatically imported during initialization. The automatic import can be suppressed using the interpreter’s -S option.

Importing this module will append site-specific paths to the module search path.

It starts by constructing up to four directories from a head and a tail part. For the head part, it uses `sys.prefix` and `sys.exec_prefix`; empty heads are skipped. For the tail part, it uses the empty string and then `lib/site-packages` (on Windows) or `lib/python|version|/site-packages` and then `lib/site-python` (on Unix and Macintosh). For each of the distinct head-tail combinations, it sees if it refers to an existing directory, and if so, adds it to `sys.path` and also inspects the newly added path for configuration files.

A path configuration file is a file whose name has the form `package.pth` and exists in one of the four directories mentioned above; its contents are additional items (one per line) to be added to `sys.path`. Non-existing items are never added to `sys.path`, but no check is made that the item refers to a directory (rather than a file). No item is added to `sys.path` more than once. Blank lines and lines beginning with `#` are skipped. Lines starting with `import` (followed by space or tab) are executed.

For example, suppose `sys.prefix` and `sys.exec_prefix` are set to `/usr/local`. The Python X.Y library is then installed in `/usr/local/lib/pythonX.Y` (where only the first three characters of `sys.version` are used to form the installation path name). Suppose this has a subdirectory `/usr/local/lib/pythonX.Y/site-packages` with three subsubdirectories, `foo`, `bar` and `spam`, and two path configuration files, `foo.pth` and `bar.pth`. Assume `foo.pth` contains the following:

    # foo package configuration

    foo
    bar
    bletch

and `bar.pth` contains:

    # bar package configuration

    bar

Then the following version-specific directories are added to `sys.path`, in this order:

    /usr/local/lib/pythonX.Y/site-packages/bar
    /usr/local/lib/pythonX.Y/site-packages/foo

Note that `bletch` is omitted because it doesn’t exist; the `bar` directory precedes the `foo` directory because `bar.pth` comes alphabetically before `foo.pth`; and `spam` is omitted because it is not mentioned in either path configuration file.

After these path manipulations, an attempt is made to import a module named `sitecustomize`, which can perform arbitrary site-specific customizations. If this import fails with an `ImportError` exception, it is silently ignored.

Note that for some non-Unix systems, `sys.prefix` and `sys.exec_prefix` are empty, and the path manipulations are skipped; however the import of `sitecustomize` is still attempted.

`site.``PREFIXES`
  A list of prefixes for site package directories

`site.``ENABLE_USER_SITE`
  Flag showing the status of the user site directory. True means the user site directory is enabled and added to sys.path. When the flag is None the user site directory is disabled for security reasons.

`site.``USER_SITE`
  Path to the user site directory for the current Python version or None

`site.``USER_BASE`
  Path to the base directory for user site directories

`PYTHONNOUSERSITE`

`PYTHONUSERBASE`

`site.``addsitedir`(sitedir, known_paths=None)
  Adds a directory to sys.path and processes its pth files.

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