Python 中的while语句 --笔记

for 循环用于针对集合中的每一个元素的一个代码块，而while循环不断地运行，直到指定的条件不满足

while  condition：

        statements

num = 1
sum = 0
while num <= 5:
    sum = num + sum
    num = num + 1
print(sum)

 输出 ： 15

使用 True 或 False 作为标志位进行条件判断，可以减少代码的运算量，使代码更加简洁

active = True
while active:
    mess = input("please input num: ")
    if mess == "quit" :
        active = False
    else:
        print(mess)

please input num: dfs
dfs
please input num: grg
grg
please input num: quit

Process finished with exit code 0

执行 break 语句，立刻跳出 while 循环体，不在执行while语句内的内容，执行while之后的语句

num = 0
sum = 0
while num <= 10:
    num = num + 1
    if num == 5:
        break
    sum = num + sum

print(sum)

输出： 10

continue 语句与 break 语句有区别，continue 语句是跳出条件判断的本层循环，break 是退出整个循环

num = 0
sum = 0
while num <= 10:
    num = num + 1
    if num == 5:
        continue
    sum = num + sum

print(sum)

输出： 61

#列表应用
stu = ['food','fruit','vegetable','moon']
stu1 = []
while stu:                      # stu 列表不为空
    stu1.append(stu.pop())      # pop() 列表的尾删函数，append() 列表的尾插函数
print("stu = " ,stu,'t',"stu1 = ",stu1,'n')

while 'fruit' in stu1:          # 在 stu1 列表中找到 'fruit'后
    stu1.remove('fruit')        # 删除 stu1 的 'fruit'
print("stu = " ,stu,'t',"stu1 = ",stu1,'n')

stu =  [] 	 stu1 =  ['moon', 'vegetable', 'fruit', 'food'] 

stu =  [] 	 stu1 =  ['moon', 'vegetable', 'food'] 

alien = {}
active = True
while active:
    key = input("please input key: ")
    val = input("please input val: ")
    alien[key] = val

    repeat = input("Would you like continue? Answer yes or no. ")
    if repeat == 'yes' or repeat == 'Yes' or repeat == 'YES':
        active = True
    elif repeat == 'no' or repeat == 'No' or repeat == 'NO':
        active = False
    else:
        print("input error")
        active = False

print("alien = ",alien)

please input key: food
please input val: beef
Would you like continue? Answer yes or no. yes
please input key: fruit
please input val: apple
Would you like continue? Answer yes or no. Yes
please input key: vegatable
please input val: fruit
Would you like continue? Answer yes or no. No
alien =  {'food': 'beef', 'fruit': 'apple', 'vegatable': 'fruit'}