python 计算一个字符串中每个字符出现的次数

def count_str(a):
    count = {}
    for i in a:
        if i in count:
            count[i] += 1
        else:
            count[i] = 1
    return count


a = 'ASAAAAAADDDDDDDDDDDDDDDFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF'
result = count_str(a)
print(result)