Simple Markov chain generator. Based partially on: https://golang.org/doc/codewalk/markov/

markov.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import random
from collections import defaultdict

class MarkovPrefix(object):

    def __init__(self, n):
        if n < 1:
            raise ValueError("MarkovPrefix requires a length of at least 1")
        self.tokens = ["" for i in xrange(n)]

    def shift(self, token):
        self.tokens = self.tokens[1:]
        self.tokens.append(token)

    def __str__(self):
        return " ".join(self.tokens)

class MarkovChain(object):

    def __init__(self, n):
        self.chain = defaultdict(list)
        self.n = n

    def feed(self, text):
        """Feed the chain a new chunk.

        Text should be chunked into logical sections -- at least one sentence.
        The prefix is reset on each call.  Chains will not (directly) continue 
        across `feed()` calls
        """
        prefix = MarkovPrefix(self.n)
        for token in text.split():
            self.chain[unicode(prefix)].append(token)
            prefix.shift(token)

    def generate(self, n):
        """Generate a block of text from the chain.

        Returns a block of text with at most `n` tokens.  May return less than
        `n` tokens if a null state is reached.
        """
        p = MarkovPrefix(self.n)
        words = []
        for i in xrange(n):
            choices = self.chain[unicode(p)]
            if len(choices) == 0:
                break    # Null state
            next = random.choice(choices)
            words.append(next)
            p.shift(next)

        return " ".join(words)