def relpath(target, link):
    """Return relative path.

    >>> relpath('/usr/share/python-foo/foo.py', '/usr/bin/foo', )
    '../share/python-foo/foo.py'
    """
    t = target.split('/')
    l = link.split('/')
    while l[0] == t[0]:
        del l[0], t[0]
    return '/'.join(['..'] * (len(l) - 1) + t)