Python function to determine if two words are Anagrams of each other

anagram.py

# Determine if an index has been checked
def index_not_in(list_of_indices, index):
    res = True
    for i in list_of_indices:
        if index == i:
            res = False
    return res

# Determine if 2 strings are anagrams
def anagram(str1, str2):
    str1 = str1.lower()
    str2 = str2.lower()
    anag = False
    checked = []
    # If the lengths are not equal, return false
    if len(str1) != len(str2):
        return False
    # Check through the 2nd string for unique instances of each item in the first string
    for index1,i in enumerate(str1):
        i_present_unique = False
        for index2, j in enumerate(str2):
            if str1[index1] == str2[index2] and index_not_in(checked, index2):
                checked.append(index2)
                i_present_unique = True
                break # No point checking the other indices
        if i_present_unique:
            anag = True
        else:
            anag = False
            break

    #print checked

    return anag

print anagram("Orchestra", "Carthorse")

print anagram("Debit card", "Bad credit")