os.path.relpath appeared in 2.6

[agramfort]

os.path.relpath appears in python 2.6
and is used eg. in nipype/pipeline/utils.py
Pipelines therefore fails on my 2.5 install.

[satra]

hey alex, i looked at python code and there appears to be a relpath for windows and a different relpath for unix. this certainly makes it more complicated.

do you have any suggestions, otherwise, i can include both relpaths perhaps in a single function and run a sub function depending on which platform things are running on.

[agramfort]

I would backport relpath with a snippet like this:

try:
    from os.path import relpath
except ImportError:
    import os
    import os.path as op
    def relpath(path, start=None):
        """Return a relative version of a path"""
        if start is None:
            start = os.curdir
        if not path:
            raise ValueError("no path specified")
        start_list = op.abspath(start).split(op.sep)
        path_list = op.abspath(path).split(op.sep)
        if start_list[0].lower() != path_list[0].lower():
            unc_path, rest = op.splitunc(path)
            unc_start, rest = op.splitunc(start)
            if bool(unc_path) ^ bool(unc_start):
                raise ValueError("Cannot mix UNC and non-UNC paths (%s and%s)" %
                                                                    (path, start))
            else:
                raise ValueError("path is on drive %s, start on drive %s"
                                             % (path_list[0], start_list[0]))
        # Work out how much of the filepath is shared by start and path.
        for i in range(min(len(start_list), len(path_list))):
            if start_list[i].lower() != path_list[i].lower():
                break
        else:
            i += 1

        rel_list = [op.pardir] * (len(start_list)-i) + path_list[i:]
        if not rel_list:
            return os.curdir
        return op.join(*rel_list)

if __name__ == '__main__':
    print relpath('/Users/alex/')

[satra]

fixed and waiting to be pulled in.