方法一：
list1 = ['a', 'a', 'b', 'c', 'c', 'c', 'c']
dict_cnt = {}
for value in list1:
dict_cnt[value...] = dict_cnt.get(value, 0) + 1
print(dict_cnt)
方法二：
list1 = ['a', 'a', 'b', 'c', 'c', 'c', 'c']
dict_cnt...= {}
for item in list1:
if item in dict_cnt: # 直接判断key在不在字典中
dict_cnt[item] += 1
else
