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pyutils / pyutils / path.py

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"""The function in this file are from:

http://www.voidspace.org.uk/python/pathutils.html

Used under BSD license. The original author is Michael Foord.
"""

import os


__all__ = ('splitall', 'relpath',)


def splitall(loc):
    """Return a list of the path components in loc. (Used by relpath_).

    The first item in the list will be  either ``os.curdir``, ``os.pardir``, empty,
    or the root directory of loc (for example, ``/`` or ``C:\\).

    The other items in the list will be strings.

    Adapted from *path.py* by Jason Orendorff.
    """
    parts = []
    while loc != os.curdir and loc != os.pardir:
        prev = loc
        loc, child = os.path.split(prev)
        if loc == prev:
            break
        parts.append(child)
    parts.append(loc)
    parts.reverse()
    return parts


def relpath(origin, dest):
    """
    Return the relative path between origin and dest.

    If it's not possible return dest.


    If they are identical return ``os.curdir``

    Adapted from `path.py <http://www.jorendorff.com/articles/python/path/>`_ by Jason Orendorff.
    """
    origin = os.path.abspath(origin).replace('\\', '/')
    dest = os.path.abspath(dest).replace('\\', '/')

    orig_list = splitall(os.path.normcase(origin))
    # Don't normcase dest!  We want to preserve the case.
    dest_list = splitall(dest)

    if orig_list[0] != os.path.normcase(dest_list[0]):
        # Can't get here from there.
        return dest

    # Find the location where the two paths start to differ.
    i = 0
    for start_seg, dest_seg in zip(orig_list, dest_list):
        if start_seg != os.path.normcase(dest_seg):
            break
        i += 1

    # Now i is the point where the two paths diverge.
    # Need a certain number of "os.pardir"s to work up
    # from the origin to the point of divergence.
    segments = [os.pardir] * (len(orig_list) - i)
    # Need to add the diverging part of dest_list.
    segments += dest_list[i:]
    if len(segments) == 0:
        # If they happen to be identical, use os.curdir.
        return os.curdir
    else:
        return os.path.join(*segments).replace('\\', '/')