s = frozenset(x.strip() for x in open(’WORD.LST’,'r’))
for w, rw in sorted([(x,x.encode(’rot13′)) for x in s if x.encode(’rot13′) in s],key=len,reverse=True) : print ‘%s : %s’%(w.ljust(20),rw)

It is nice, every once in a while, to cram as much functionality as possible into the fewest lines of code imaginable.

“I think the author invented the term, because the only reference I found to ‘rotonym’ came from his site.”

I think I did, also; likely (found and named them) out of the same drive for interesting exercises that motivated you to code your own script to find them.

words = set([line.strip() for line in file(’WORD.LST’, ‘r’)])
rotwords = set([word.encode(’rot13′) for word in words]) & words
for word in sorted(rotwords, key=len, reverse=True):
print word.encode(’rot13′), word

With sorted printing, and maximal work done by native code.

Neat, but I also removed equivalent pairs and sorted the output by length of word.

>>> words = set([w.strip().decode(’ascii’, ‘ignore’) for w in file(’/usr/share/dict/words’)])
>>> print [(w, w.encode(’rot13′)) for w in words if w.encode(’rot13′) in words]

First line reads the dictionary while ignoring unicode encoding errors (unfortunately necessary on my Ubuntu system). Second line gets the rotonyms (I don’t like the duplicated encode() call in that line).

Favourite rotonyms from my dictionary:
Robyn - Ebola
sync - flap
rail - envy
one - bar
Green - Terra

In conclusion, I