# 26.11 `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/python2.5/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` are executed.

For example, suppose `sys.prefix` and `sys.exec_prefix` are set to /usr/local. The Python 2.5 library is then installed in /usr/local/lib/python2.5 (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/python2.5/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 directories are added to `sys.path`, in this order:

    /usr/local/lib/python2.3/site-packages/bar
    /usr/local/lib/python2.3/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.