5 循环控制

1 while 循环

语法

while  条件:
        执行代码。。。

简单吧, while 就是当的意思，当山峰没有棱角的时候，当河水。。。，sorry , while 指当其后面的条件成立，就执行while下面的代码

从0打印到100的程序，每循环一次，+1

#!/usr/bin/env python 
#$ coding:utf-8 $
#__Author__:Peter Du

count = 0
while count <=100:
    print("loop",count)
    count += 1

print("----loop end----")

结果

count  = 0
while count<= 100:
    if count % 2 ==0:
        print("loop",count)
    count += 1
print("----loop end----")

#运行结果
loop 82
loop 84
loop 86
loop 88
loop 90
loop 92
loop 94
loop 96
loop 98
loop 100
----loop end----

#第50次不打印，第60-80打印对应值的平方
count = 0
while count <= 100:
    if count == 50:
        pass
    elif 60 <= count <= 80:
        print("loop",count**2)
    else:
        print("loop",count)
    count += 1

print("----loop end----")

#运行结果
loop 46
loop 47
loop 48
loop 49
loop 51
loop 52
loop 53
loop 54
loop 55
loop 56
loop 57
loop 58
loop 59
loop 3600
loop 3721
loop 3844
loop 3969
loop 4096
loop 4225

2 死循环：dead loop

有一种循环叫死循环，一经运行，就一直运行

while 是只要后边条件成立，（也就是条件结果为真）就一直执行，怎么让条件为真呢？

count = 0
while True: #True本身就是真呀

    print("你是风儿我是沙,缠缠绵绵到天涯...",count)
    count +=1

3 循环终止语句

如果在循环过程中，因某些原因，不想循环，需用break 或者 continue 语句

break 用于结束一个循环，跳出循环体执行循环后面的语句
continue 和break 有点类似,区别在于continue 只是终止本次循环，接着还执行后面的循环，break 则完全终止循环

break 例子

count = 0
while count <= 100:
    print("loop",count)
    if count == 5:
        break
    count += 1
    
print("---out of while loop---")

#运行结果
loop 0
loop 1
loop 2
loop 3
loop 4
loop 5
---out of while loop---

continue 案例

count = 0
while count <= 100:
    print("loop",count)
    if count == 5:
        continue
    count += 1

print("---out of while loop---")

#运行结果

loop 0
loop 1
loop 2
loop 3
loop 4
loop 5
loop 5
loop 5
loop 5
loop 5
loop 5     # 一直循环下去
...

continue 案例2

count = 0
while count <= 100:
    count += 1
    if count > 5 and count <95:
        continue
    print("loop ",count)

#运行结果
loop  1
loop  2
loop  3
loop  4
loop  5
loop  95
loop  96
loop  97
loop  98
loop  99
loop  100
loop  101

Process finished with exit code 0

3 猜年龄

练习1

age = 22
n=0
while n < 3:
    print("input you age")
    user_age = int(input())
    if user_age < age:
        print("small")
    elif user_age > age:
        print("big")
    else:
        print("bingo")
        break
    n += 1

    if n==3:
        choice = input("请问你还想继续游戏吗？y|n")
        if choice=='y':
            n=0
        else:
            break
#运行结果

input you age
10
small
input you age
30
big
input you age
22
bingo

Process finished with exit code 0

练习2

from random import randint
num = randint(1,100)

print("请输入你的数字")

bingo = False

while bingo == False:
    user_num = int(input())

    if user_num < num:
        print("small")
    elif user_num > num:
        print("big")
    else:
        print("bingo")
        bingo = True

#运行结果
请输入你的数字
10
small
50
big
30
small
40
big
35
bingo

Process finished with exit code 0