1.

from collections import Counter

string = '1212ababABAB'
s = Counter(string)
print(s)

2.

string = '1212ababABAB'
s = {x: string.count(x) for x in set(string)}   # 用的是字典推導式和str自帶的str.count方法
print(s)

3.

string = '1212ababABAB'

def fun(s):
    # 去除字串中的空格
    s = list(''.join(s.split()))
    # 去重
 

    s1 = set(s)
    l = list(s1)
    dic = {}
    for a in range(len(l)):
        num = 0
        for i in reversed(range(len(s))):
            if l[a] == s[i]:
                num = num + 1
                s.pop(i)
        dic[l[a]] = num
    return dic

t = fun(string)
print(t)