Group by ranges in Python

gistfile1.py

import itertools

def group_ranges(values, ranges):
    # Utilities
    split_at = lambda f: lambda l: \
        (itertools.takewhile(lambda e: not f(e), l), itertools.dropwhile(lambda e: not f(e), l))

    # Reducer
    def f((values, acc), delim):
        (pre, post) = split_at(lambda e: e >= delim)(values)
        return (list(post), acc + [list(pre)])

    # Evaluation
    (leftovers, groups) = reduce(f, ranges, (sorted(values), []))

    return groups + [leftovers]

# Demo
test_data = range(0, 15)
test_ranges = [2, 5, 9]
# Think ranges = [(0, 2), (2, 5), (5, 9)]

print group_ranges(test_data, test_ranges)