1 from os.path import join, normcase, abspath, sep

     2 

     3 def safe_join(base, *paths):

     4     """

     5     Joins one or more path components to the base path component intelligently.

     6     Returns a normalized, absolute version of the final path.

     7 

     8     The final path must be located inside of the base path component (otherwise

     9     a ValueError is raised).

    10     """

    11     # We need to use normcase to ensure we don't false-negative on case

    12     # insensitive operating systems (like Windows).

    13     final_path = normcase(abspath(join(base, *paths)))

    14     base_path = normcase(abspath(base))

    15     base_path_len = len(base_path)

    16     # Ensure final_path starts with base_path and that the next character after

    17     # the final path is os.sep (or nothing, in which case final_path must be

    18     # equal to base_path).

    19     if not final_path.startswith(base_path) \

    20        or final_path[base_path_len:base_path_len+1] not in ('', sep):

    21         raise ValueError('the joined path is located outside of the base path'

    22                          ' component')

    23     return final_path