基本运算符补充,流程控制if判断与while循环

1. 算术运算

print(10 / 3) 

print(10 // 3) 

print(10 ** 2) 

2. 赋值运算 

增量赋值 

age=18 

age+=1

age=age + 1 

print(age) 

age=18 

age/=3 

age=age/3 

print(type(age)) 

age**=2 

age=age**2 

交叉赋值 

x=10 

y=20 

temp=x 

x=y 

y=temp

print(x,y)

链式赋值
x=10

y=x

z=y

x=y=z=10

print(id(x))

print(id(y))

print(id(z))

 

解压赋值

l=[1.2,2.2,3.3,4.4,5.5] 

a=l[0] 

b=l[1] 

c=l[2] 

d=l[3] 

e=l[4] 

a,b,c,d,e=l 

a,b,c,d,e,f=l 

a,b,c,d=l 

print(a,b,c,d,e)

l=[1.2,2.2,3.3,4.4,5.5] 

a,b,*_=l 

print(a,b) 

a,*_,b=l 

print(a,b)

*_,a,b=l

print(a,b)

 

流程控制之while循环

 

基本语法:

while 条件:

　　代码1

　　代码2

　　代码3

　　...

示范
name_of_bk='egon'
pwd_of_bk='123'

tag=True
while tag:
    inp_name=input('your name>>: ')
    inp_pwd=input('your password>>: ')
    if inp_name == name_of_bk and inp_pwd == pwd_of_bk:
        print('login successful')
        tag=False
    else:
        print('username or password error')

    print('other code...')

II: while+break:break代表结束本层循环
示范：
while True:
    print(1)
    break
    print(2)
    print(3)

name_of_bk='egon'
pwd_of_bk='123'

while True:
    inp_name=input('your name>>: ')
    inp_pwd=input('your password>>: ')
    if inp_name == name_of_bk and inp_pwd == pwd_of_bk:
        print('login successful')
        break
    else:
        print('username or password error')

    print('other code......')


III: while + continue: continue代表结束本次循环，直接进入下一次
示范
count=1
while count < 6:
    if count == 3:
        count+=1
        continue
    print(count)
    count+=1


输错三次退出
name_of_bk='egon'
pwd_of_bk='123'

count=0
while True:
    if count == 3:
        print('输错的次数过多。。。')
        break
    inp_name=input('your name>>: ')
    inp_pwd=input('your password>>: ')
    if inp_name == name_of_bk and inp_pwd == pwd_of_bk:
        print('login successful')
        break
    else:
        print('username or password error')
        count+=1 #count=3 输错3次


IV:while + else
count=0
while True:
    if count == 10:
        break
    print(count)
    count+=1

else:
    print("else的子代块只有在while循环没有被break打断的情况下才会执行")



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

else:
    print("else的子代块只有在while循环没有被break打断的情况下才会执行")

name_of_bk='egon'
pwd_of_bk='123'

count=0
tag=True
while tag:
    if count == 3:
        print('输错的次数过多。。。')
        break
    inp_name=input('your name>>: ')
    inp_pwd=input('your password>>: ')
    if inp_name == name_of_bk and inp_pwd == pwd_of_bk:
        print('login successful')
        while tag:
            print("""
            0 退出
            1 购物
            2 支付
            3 查看购物
            """)
            cmd=input('>>>: ')
            if cmd == '0':
                tag=False
                continue
            if cmd == '1':
                print('购物。。。。。。。')
            elif cmd == '2':
                print('支付。。。。。')
            elif cmd == '3':
                print('查看购物车')
            else:
                print('输入错误的指令')
    else:
        print('username or password error')
        count+=1 #count=3 输错3次