Modules, strings, lists, hashes, exceptions


import string, sys

concordance = {}

for line in sys.stdin.readlines():
    for word in string.split(line):
        try:
            concordance[word] = concordance[word] + 1
        except KeyError:
            concordance[word] = 1

keys = concordance.keys()
keys.sort()

for key in keys:
    print key, concordance[key]

Python Library Reference has pages and pages of modules
Many third party modules available