How to optimize this Python code (from ThinkPython, Exercise 10.10)

Question

I\'m working through Allen Downey\'s How To Think Like A Computer Scientist, and I\'ve written what I believe to be a functionally correct solution to Exercise 10.1

Answer 1

An alternate version:

with open('words.txt') as inf:
    words = set(wd.strip() for wd in inf)

word_gen = ((word, word[::2], word[1::2]) for word in words)
interlocked = [word for word,a,b in word_gen if a in words and b in words]

On my machine this runs in 0.16 seconds and returns 1254 words.

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Edit: as pointed out by @John Machin at Why is this program faster in Python than Objective-C? this can be further improved by lazy execution (only perform the second slice if the first results in a valid word):

with open('words.txt') as inf:
    words = set(wd.strip() for wd in inf)
interlocked = [word for word in words if word[::2] in words and word[1::2] in words]

This drops execution time by a third, to 0.104 seconds.