Checking if two strings are anagrams

Question

I have a piece of code that checks if two strings are anagrams. I would like this to be as pythonic as possible.

def are_two_string_anagram(string1, string2):
 if len(string1) != len(string2):
 return False
 def char_count(string):
 char_count = {}
 for s in string:
 char_count[s] = char_count.get(s, 0) + 1
 return char_count
 chr_count = char_count(string1)
 chr1_count = char_count(string2)
 return chr_count == chr1_count
string1 = "mary"
string2 = "yram"
print(are_two_string_anagram(string1, string2))
string1 = "albert"
string2 = "abelrt"
print(are_two_string_anagram(string1, string2))
string1 = "something"
string2 = "anotherus"
print(are_two_string_anagram(string1, string2))

• Curt F.: Related: codereview.stackexchange.com/questions/96475/…

Answer 1

Most python users would just use sorted(string1) == sorted(string2). That's \$O(n log n)\,ドル which is not that much worse than your \$O(n)\$ solution.

But the code you've actually written is just a reimplementation of:

collections.Counter(string1) == collections.Counter(string2)

That said, your short-circuit if the lengths mismatch is a good idea no matter which implementation you use.

There are some style issues that jump out with your implementation:

• char_count doesn't have a pressing need to be a nested function, I would put it at top level.
• Don't have a local variable named char_count inside the same-named function.
• Don't cross numbers like chr_count = char_count(string1);chr1_count = char_count(string2). If you need numbered variables, use the same number for all transformed forms also.

For your demonstration code, I would have written:

def test_two_string_anagrams():
 assert are_two_string_anagram("mary", "yram")
 assert are_two_string_anagram("albert", "abelrt")
 assert are_two_string_anagram("something", "anotherus")

Or possibly:

def test_two_string_anagrams():
 for s1, s2 in [
 ("mary", "yram"),
 ("albert", "abelrt"),
 ("something", "anotherus"),
 ]:
 assert are_two_string_anagram(s1, s2)

That way it can be run directly with py.test (and possibly other harnesses, I know the standard unittest requires wrapping them in a dummy class, but I haven't used any others).

• toy: What if I cannot use collections.Counter? is my implementation correct? I was asked for a job interview that I can only use basic functions.
• o11c: @toy Yeah, you've written the same algorithm as collections.Counter uses.
• CodesInChaos: anotherus should return false.