下面三个问题能想到初步的方法，请具体讲解

能想到lower转化小写，replace替换标点符号，split提取单词

能想到使用split输入信息读取

私信一下吧，我给你发代码

## 问题1
sen=input()
sen1=sen.lower().replace(',',' ').split(' ')
dic={}
for k in sen1:
    dic[k]=dic.get(k,0)+1
for i in dic.items():
    print(i)

## 问题2
stu={}
i=0
while i<3:
    a=input("输入学号，姓名，年龄，空格分隔：")
    numb,nm,age=a.split(' ')
    stu[int(numb)]=(nm,int(age))
    i=i+1

print(sorted(stu.items(), key = lambda kv:(kv[1][1], kv[0])))


## 问题3
up={'u1':'p1','u2':'p2','u3':'p3'}
while 1:
    u=input("输入用户名：")
    if u in up:
        p=input("输入密码：")
        if p== up[u]:
            print("login Success")
        else:
            print("Password Error")
    else:
        print("Username Error")
    

def function1():
    sen = input("输入文本:")
    arr = sen.split(' ')
    count_dict = {}
    for i in arr:
        count_dict[i] = count_dict.get(i, 0) + 1
    items = count_dict.items()
    for k, v in items:
        print(k, v)


def function2():
    stu = {}
    for i in range(3):
        information = input(f"输入第{i + 1}个学生的信息(学号、姓名、年龄 用空格隔开):")
        arr = information.split(' ')
        stu[eval(arr[0])] = [arr[1], eval(arr[2])]
    items1 = sorted(stu.items(), key=lambda x: x, reverse=False)
    for k, v in items1:
        print("学号:", k, "姓名:", v[0], "年龄:", v[1])
    items2 = sorted(stu.items(), key=lambda x: x[1][1], reverse=False)
    new_stu = {}
    for k, v in items2:
        new_stu[k] = v
    print(new_stu)


def function3():
    user = {"10086": "123", "10087": "456", "10088": '789'}
    while True:
        name = input("输入用户名:")
        if name == 'END':
            break
        if name not in user:
            print("Username Error")
            continue
        pwd = input("输入密码:")
        if pwd == 'END':
            break
        if pwd != user[name]:
            print("Password Error")
        if pwd == user[name]:
            print("Login Success")


if __name__ == '__main__':
    function1()
    function2()
    function3()

3个函数对应你的3个问题，有用的话点一下采纳

如果需要java代码实现，我可以提供