while & for & continue & break

1. while循环：

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练习一：用while语句求1-100的和

i = 1
m = 0
while i <= 100:
    m += i
    i += 1
print("1-100的和为: %d" % m)

练习二：用while语句完成猜数字游戏

import random

num = random.randint(1, 100)
times = 0

while True:
    guess = int(input("猜一猜我心里想的数字, 1-100之间的随机整数哦！"))
    times += 1
    if guess == num:
        print(f"恭喜你！猜中了！这是您第{times}次猜测！")
        break
    elif guess > num:
        print(f"不对哦！猜大了！这是您第{times}次猜测！再来试试吧！")
    else:
        print(f"不对哦！猜小了！这是您第{times}次猜测！再来试试吧！")

import random

num = random.randint(1, 100)
times = 0
whether_continue = True

while whether_continue:
    guess = int(input("猜一猜我心里想的数字, 1-100之间的随机整数哦！"))
    times += 1
    if guess == num:
        print(f"恭喜你！猜中了！这是您第{times}次猜测！")
        whether_continue = False  # 不使用break
    elif guess > num:
        print(f"不对哦！猜大了！这是您第{times}次猜测！再来试试吧！")
    else:
        print(f"不对哦！猜小了！这是您第{times}次猜测！再来试试吧！")

练习三：用嵌套while语句打印出九九乘法表

i = 1
while i <= 9:
    j = 1
    while j <= i:
        print(f"{j}*{i}={j*i}", end='\t')
        j += 1
    print()  # print空内容就是输出一个换行
    i += 1

总结：while循环可以帮助我们方便的控制循环的次数，不管是内层循环还是外层循环，我们都需要一个变量来控制循环的次数！

 

 

2. for循环

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练习一：定义一个变量name = "itheima is a brand of itcast"，使用for循环统计里面有多少个字母a？

name = "itheima is a brand of itcast"
count = 0
for each in name:
    if each == "a":
        count += 1
print(f"{name}中一共有{count}个'a'")

Range语句：

练习二：有几个偶数？

num = 100
count = 0
for i in range(1, num):
    if i % 2 == 0:
        count += 1
print("1-100(不包含100), 一共有%d个偶数" % count)

变量作用域:

练习三：用for循环打印九九乘法表

for i in range(1, 10):
    for j in range(1, i+1):
        print(f"{j}*{i}={j*i}", end='\t')
    print()

 

 

3. continue和break

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总结：break是直接结束循环，continue是结束本次循环！

需要注意的是，当break和continue用在内层循环时，只会对内层循环造成影响！

练习一：发工资

import random

money = 10000
for i in range(1, 21):
    score = random.randint(1, 10)
    if score < 5:
        print(f"员工{i}, 绩效分{score}, 低于5, 不发工资, 下一位。")
        continue
    else:
        if money != 0:
            money -= 1000
            print(f"向员工{i}发放工资1000元, 账户余额还剩余{money}元。")
            if money == 0:
                print("工资发完了, 下个月领取吧。")
                break