def getPermutations(string, prefix=""):
if len(string) == 1:
yield prefix + string
else:
for i in xrange(len(string)):
for perm in getPermutations(string[:i] + string[i+1:], prefix+string[i]):
yield perm
Or without an accumulator:
def getPermutations(string):
if len(string) == 1:
yield string
else:
for i in xrange(len(string)):
for perm in getPermutations(string[:i] + string[i+1:]):
yield string[i] + perm