gistfile1.py

import os
from collections import defaultdict
# http://www.reddit.com/r/learnpython/comments/yn52v/noob_advice_please_best_way_to_approach_this/

def normalized_filenames(dirname, func):
    """Builds a map from the normalized filename to the actual filename for
    all the filenames in the directory and its sub-directories.
    """
    # Use lists to hold values because more than 1 file can have the same key.
    d = defaultdict(list)
    for root, dirs, files in os.walk(dirname):
        for name in dirs + files:
            p = os.path.join(root, name)
            d[func(p)].append(p)
    return d


def keyfunc(filename):
    """The key/normalizing function to use on every filename. Returns the
    lower-case version of the last part of the path minus extension.
    """
    name = os.path.basename(filename)
    name = os.path.splitext(name)[0]
    name = name.lower()
    return name


startdir = '/path/to/hd'
lowercase_names_map = normalized_filenames(startdir, keyfunc)


for picname in spreadsheet:
    normname = keyfunc(picname)
    foundnames = lowercase_names_map.get(normname, [])
    print "%s (%s) matches %r" % (picname, normname, foundnames)