while 循环

---恢复内容开始---

死循环

while True:    #会执行到天荒地老、海枯石烂
    print("ok")

循环

count = 0
while count < 10:
    print(count)
    count +=1

使用while循环输出1 2 3 4 5 6  8 9 10

age = 1
while age < 11:
    if age == 7:
        pass
    else:
        print(age)
    age +=1

输出1-100的所有数的和

age = 1
n =0
while age < 101:
    age +=1
    n = n + age
print(n)

输出1-100内所有的奇数

age = 1
while age < 101:
    if age % 2 == 1:
        pass
    else:
        print(age)
    age +=1

输出1-100内所有的偶数

age = 1
while age < 101:
    if age % 2 == 1:
        print(age)
    else:
        pass
    age +=1

求1-2+3-4+5.....99的和

age = 1
n =0
while age < 100:
    if age % 2 == 0:
        n = n - age
    else:
        n = n + age
    age += 1
print(n)

 continue ：跳出本次循环，进行下一次循环

count = 0
while count <5:
    print(count)
    count +=1
    continue
    print("1111")  #这句代码是不会执行的
print("end")
执行结果：
0
1
2
3
4
end

break：终止循环

count = 0
while count <5:
    print(count)
    count +=1
    break           #终止整个循环，执行循环外的语句
    print("1111")   #这句代码没有被执行
print("end")
执行结果：
0
end

用户三次登录

count = 0
while count < 3:
    user = input("请输入用户名：")
    pwd = input("请输入密码：")
    if user == "root"  and pwd == "root":
        print("登录成功")
        break
    else:
        print("用户或密码错误")
    count +=1