Does what it says on the box. Inspired by http://xkcd.com/936/

random_passphrase_generator.py

#!/usr/bin/env python
from __future__ import print_function
import argparse
import math
import random 
import string
import sys
 
class PassGen:
    def __init__(self, dictionary, connectives, minimum_word_length, no_white_space=False):
        self.dictionary_file = open(dictionary, "r")
        self.connective_dictionary_file = open(connectives, "r")
        self.minimum_word_length = minimum_word_length
        self.join_character = '_' if no_white_space else ' '
 
        self.words = [w.rstrip() for w in self.dictionary_file if len(w) >= self.minimum_word_length]
        self.joins = [w.rstrip() for w in self.connective_dictionary_file]
        self.symbols = string.punctuation
        self.digits = string.digits
 
    def generate(self, count=1, length=2):
        return [self.__compose_phrase(length) for x in range(count)]
 
    def entropy(self, length):
        return math.log((len(self.joins) * len(self.words)) ** length. 2)
 
    def __compose_phrase(self, length):
        # word symbol word number
        return self.join_character.join([
            self.join_character.join((
                random.choice(self.joins),
                random.choice(self.words)
            ))
            for x in range(length)
        ])
 
 
if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument('--dictionary', '-d', default="/usr/share/dict/words")
    parser.add_argument('--connectives', '-D', default="/usr/share/dict/connectives")
    parser.add_argument('--count', '-c', default=1, type=int)
    parser.add_argument('--minimum-word-length', '-m', default=10, type=int)
    parser.add_argument('--no-white-space', '-W', action="store_true")
    parser.add_argument('--length', '-l', type=int, default=2)
 
    args = parser.parse_args()
    pg = PassGen(args.dictionary, args.connectives, args.minimum_word_length, args.no_white_space)
 
    print("Generating %d passwords with ~%d bits of entropy" % (args.count, pg.entropy(args.length)), file=sys.stderr)
 
    print("\n".join(pg.generate(int(args.count), args.length)))