python自动判断输入字符串单个字符出现次数

str_input = input("请输入英语字符")

dict_1 = {}

str_2 = str_input.replace(' ','')

#print("第一次处理结果：%s"%str_2)

str_3 = set(str_2)

#print("第二次处理结果：%s"%str_3)

for test in str_3:
        dict_1[test] = 0

for key, values in dict_1.items():
        num = 0
        for str_4 in str_input:
                if key==str_4:
                        num+=1
        dict_1[key] = num
for key, values in dict_1.items():
        print("字母%s  出现次数为%s"%(key,values))