word shifts

[Gabriel Genellina]

En Sun, 04 May 2008 02:17:07 -0300, dave <squareswallower at invalid.com> escribió:

> Hello,
>
> I made a function that takes a word list (one word per line, text file)
> and searches for all the words in the list that are 'shifts' of
> eachother.  'abc' shifted 1 is 'bcd'
>
> Please take a look and tell me if this is a viable solution.
>
>  def shift(word, amt):
> 	ans = ''
> 	for letter in word:
> 		ans = ans + chr((ord(letter) - ord('a') + amt) % 26 + ord('a'))
> 	return ans
>
> def fileshift(x):
> 	fin = open(x)
> 	d = {}
> 	for line in fin:
> 		d[line.strip()] = [1]
> 		for i in range(1, 26):
> 			ite = shift(line.strip(), i)
> 			if ite in d:
> 				print ite
>
>
> Any tips/suggestions/critiques greatly appreciated.. I'm trying to
> teach myself Python (and still beginning) and would love any helpful
> info.

First, looking at the code, you're evaluating line.strip() a lot of times; I'd avoid it.
Looks like you're using a dictionary just for the keys - the set type is more adequate here (see http://docs.python.org/lib/types-set.html ). In any case, I'd use a value like None instead of [1]
But I'd use a different algorithm. Instead of generating all posible shifts for a given word, I'd substract the newly read word from each previous words (here, "substract two words" means substract the character code for corresponding positions, modulo 26). Shifted words, when substracted, have the same number on all positions.

-- 
Gabriel Genellina