1.3if判断语句+while和for循环语句+购物车作业

1、if 语句

if userame=_usename and password=_password:

print("welcome user {name} login...").fomat(name=username)

elif userame=_usename and password!=_password:

print("hello user {name} ,your password is wrong!").fomat(name=username)

else:

print("invalid username and password!")

#换行为python的功能表示子代码（即次级代码）

2、while循环语句

while True:

break                         #跳出循环

pass                          #什么都不做

else:

3、for循环语句

for i in range(0,10,3):    #i从0开始循环10次，隔3个开始一次

continue                        #直接下一循环

break                            #跳出循环

else:                              #for正常走完了之后执行（即没中途break）

4、购物车作业

购物车功能说明：输入工资，显示商品，输入商品编号购买商品

product_list=[
    ("book",100),
    ("coffee",50),
    ("table",200),
    ("shit",10),
    ("computer",10000)
]
shop_list=[]
shop_money=0

while True:
    salary = input("input your salary>>>")
    if salary.isdigit():
        salary = int(salary)
        break
    else:
        print("you must input number!")

while True:
    if salary == 0:
        print("your money left 0 yuan,break")
        break
    if shop_list != []:
        print("the goods you have picked:%s"%shop_list)
    print("your salary balance %d yuan." % salary)
    for goods in enumerate(product_list):
        print(goods)
    num=input("what do you want to bug?(you can input 0-4,or \"q\" to quit)")
    if num.isdigit():
        num = int(num)
        if num >=0 and num <=4:
            price = product_list[num]
            if price[1] <= salary:
                salary -=price[1]
                shop_list.append(price[0])
                shop_money +=price[1]
            else:
                print("you have no much money!")

        else:
            print("input wrong digit!")

    elif num=="q":
        break

    else:
        print("input wrong digit!")

print("the goods you have picked:%s"%shop_list)
print("it will cost you {cost} yuan,and your salary will balance {yuan} yuan".format(cost=shop_money,yuan=salary))