Count together the CSV rows' last columns and use the first n rows as the key

csvsum.py

#!/usr/bin/python

# Count together the CSV rows' last columns and use the first n rows as the key.
# Use cut to crop the key space, e.g.
# $ cut -d\; -f 3-4,8 | csvsum.py


import sys

sums = {}
total = 0

for line in sys.stdin:
    fields = [s.strip('"') for s in line.rstrip().split(";")]
    try:
        count = int(fields.pop())
        total = total + count
        key = " ".join(fields)
        try:
            sums[key] = sums[key] + count
        except KeyError:
            sums[key] = count
    except ValueError:
        pass

for key in sums.viewkeys():
    print key + ": " + str(sums[key]) + " (" + str(sums[key]*100/total) + "%)"