Checking if two strings are permutations of each other in Python

Question

I\'m checking if two strings a and b are permutations of each other, and I\'m wondering what the ideal way to do this is in Python. From the Zen of

Answer 1

Here are some timed executions on very small strings, using two different methods:
1. sorting
2. counting (specifically the original method by @namin).

a, b, c = 'confused', 'unfocused', 'foncused'

sort_method = lambda x,y: sorted(x) == sorted(y)

def count_method(a, b):
    d = {}
    for x in a:
        d[x] = d.get(x, 0) + 1
    for x in b:
        d[x] = d.get(x, 0) - 1
    for v in d.itervalues():
        if v != 0:
            return False
    return True

Average run times of the 2 methods over 100,000 loops are:

non-match (string a and b)

$ python -m timeit -s 'import temp' 'temp.sort_method(temp.a, temp.b)'
100000 loops, best of 3: 9.72 usec per loop
$ python -m timeit -s 'import temp' 'temp.count_method(temp.a, temp.b)'
10000 loops, best of 3: 28.1 usec per loop

match (string a and c)

$ python -m timeit -s 'import temp' 'temp.sort_method(temp.a, temp.c)'
100000 loops, best of 3: 9.47 usec per loop
$ python -m timeit -s 'import temp' 'temp.count_method(temp.a, temp.c)'
100000 loops, best of 3: 24.6 usec per loop

Keep in mind that the strings used are very small. The time complexity of the methods are different, so you'll see different results with very large strings. Choose according to your data, you may even use a combination of the two.