gistfile1.py

import sys 
from random import choice

MAXWORDS = 10000        # Max words to output
NPREF = 2               # Number of prefix words
NONWORD = '\n'          # Sentinel word

table = {} # {(p1,p2) : [s1, s2, s3]}
prefix = tuple([NONWORD for i in range(NPREF)])
wordlist = sys.stdin.read().split()

# shiftTuple((1,2,3), 4) => (2,3,4)
def shiftTuple(tup, elm):
        return tuple(list(tup)[1:] + [elm])

##################################################

# Build prefix table
for word in wordlist:
        if prefix not in table: table[prefix] = []
        table[prefix].append(word)
        prefix = shiftTuple(prefix, word)
table[prefix].append(NONWORD)

# Generate output
prefix = tuple([NONWORD for i in range(NPREF)])
for i in range(MAXWORDS):
        if prefix in table: 
                word = choice(table[prefix])
                if word == NONWORD: break
                print word
        prefix = shiftTuple(prefix, word)