A list of strings that specifies the search path for modules. Initialized from the environment variable PYTHONPATH, plus an installation-dependent default.
As initialized upon program startup, the first item of this list,
path, is the directory containing the script that was used to
invoke the Python interpreter. If the script directory is not
available (e.g. if the interpreter is invoked interactively or if the
script is read from standard input),
path is the empty string,
which directs Python to search modules in the current directory
first. Notice that the script directory is inserted before the
entries inserted as a result of PYTHONPATH.
A program is free to modify this list for its own purposes.
Changed in version 2.3: Unicode strings are no longer ignored.