longest_col.py

import csv, sys
lengths = {}
with open(sys.argv[1], 'rt') as f:
    reader = csv.DictReader(f, delimiter='|')
    for index, row in enumerate(reader):
        if index == 0:
            for heading in row.keys():
                lengths[heading] = 0
        for column in row.keys():
            if (len(row[column]) > lengths[column]):
                lengths[column] = len(row[column])
    print lengths