Fast algorithm to find anagram of a word using preindex of words

anagram_prime.py

#!/usr/bin/env python3
# Author: Supreet Sethi <supreet.sethi@gmail.com>
# License: Creative Commons BY-SA 2.0

from string import ascii_lowercase

WORDSFILE = '/usr/share/dict/words' # this is specific to mac os


def alphabet_prime_data():
	prime = []
	for num in range(2,107):
  		if all(num%i!=0 for i in range(2,num)):
  			prime.append(num)

  	return dict(zip(ascii_lowercase, prime[:len(ascii_lowercase)]))


def hash_word(word, alpha):
	val = 1
	for c in ''.join(filter(str.isalnum, word).lower()): # remove special character and lower case before hashing
		val = alpha[c] * val
	return val

def preindex_words(fd, alpha):
	index = {}
	for line in fd.readlines():
		line = line.strip()
		h = hash_word(line, alpha)
		index.setdefault(h, []).append(line)
	return index


def find_anagram(word, index, alpha):
	hash = hash_word(word, alpha)
	return list(filter(lambda x: x != word, index[hash]))

alpha = alphabet_prime_data()
fd = open(WORDSFILE)

index = preindex_words(fd, alpha)

print(find_anagram('salt', index, alpha))