SaltyCrane Blog — Notes on Javascript and web development

os.path.relpath() source code for Python 2.5

Today I needed to use the os.path.relpath() function. However this function was introduced in Python 2.6 and I am using Python 2.5 for my project. Luckily, James Gardner has written a version that works with Python 2.5 (on Posix systems (which mine is (Linux))). His relpath function is part of his BareNecessities package. You can view the documentation here.

Here is James Gardner's relpath function:

from posixpath import curdir, sep, pardir, join

def relpath(path, start=curdir):
    """Return a relative version of a path"""
    if not path:
        raise ValueError("no path specified")
    start_list = posixpath.abspath(start).split(sep)
    path_list = posixpath.abspath(path).split(sep)
    # Work out how much of the filepath is shared by start and path.
    i = len(posixpath.commonprefix([start_list, path_list]))
    rel_list = [pardir] * (len(start_list)-i) + path_list[i:]
    if not rel_list:
        return curdir
    return join(*rel_list)

Comments


#1 Pamela McA'Nulty commented on :

Fixed to deal with missing posixpath functions, works in 2.4 too pam

from posixpath import curdir, sep, pardir, join, abspath, commonprefix

def relpath(path, start=curdir):
    """Return a relative version of a path"""
    if not path:
        raise ValueError("no path specified")
    start_list = abspath(start).split(sep)
    path_list = abspath(path).split(sep)
    # Work out how much of the filepath is shared by start and path.
    i = len(commonprefix([start_list, path_list]))
    rel_list = [pardir] * (len(start_list)-i) + path_list[i:]
    if not rel_list:
        return curdir
    return join(*rel_list)