Python之路【第四篇】Python基础2

一、格式化输出

按要求输出信息

name=input("name:")
age=int(input("age:"))
job=input("job:")
salary=input("salary:")

if salary.isdigit(): #长得像不像数字，比如200d，‘200’
    salary=int(salary)
else:
    exit("must input digit!")

msg='''
---------info of %s-------------
Name: %s
Age: %d
Job: %s
Salary: %f
You'll retire in %s years.
-----------end------------------
'''%(name,name,age,job,salary,65-age)
print(msg)

二.循环

登录三次，不成功打印error

（1）for循环

#passed_authentication=False
for i in range(3):
    username=input("username:")
    passwd=input("password:")
    if username=="admin" and passwd=="admin":
#        passed_authentication=True
        print("Welcome!")
        break  #跳出，中断  break for后就不会执行后面的else语句
    else:
        print("try again!")
else: #只要上面的循环正常执行完毕，中间没被打断，就会执行else语句
#if not passed_authentication:
    print("error!")

（2）while循环

counter=0
while counter<3:
    username=input("username:")
    passwd=input("password:")
    if username=="admin" and passwd=="admin":
        print("Welcome!")
        break  #跳出，中断  break for后就不会执行后面的else语句
    else:
        print("try again!")
    counter += 1
    if counter==3:
         keep_going_choice=input("还想玩吗？[y/n]")
         if keep_going_choice=='y':
              counter=0
else:
    print("error!")

三、练习（购物车程序）

goods_list=[('iphone',6000),('mac',9000),('coffee',32),('python book',100),('bicycle',1500)]
#print(len(goods_list))
cart=[]
saving=input("please input your saving:")
if saving.isdigit():
    saving=int(saving)
    while True:
        # 打印商品内容
        for i,v in enumerate(goods_list,1):  #for后面可以接列表、元祖、字典
            print(i,v)
        # 引导用户选择商品
        choice=input("请输入您要购买的商品序号[退出：q]:")
        # 验证输入是否合法
        if choice.isdigit():
            choice=int(choice)
            if choice > 0 and choice <= len(goods_list) :
                # 通过choice取出用户选择的商品
                p_item=goods_list[choice-1]
                print(p_item)
                # 如果余额充足，用余额减去选择的商品的价格，并将该商品加入购物车
                if p_item[1] < saving:
                    saving-=p_item[1]
                    print('还剩%s元'%saving)
                    cart.append(p_item)
                else:
                    print('余额不足，还剩%s元'%saving)
            else:
                print('编码不存在！')
        elif choice=='q':
            print('-----您已经购买如下商品------')
            # 循环遍历购物车的商品，注意：购物车存放的是已买商品
            for i in cart:
                print(i)
            print('您还剩%s元'%saving)
            break
        else:
            print('非法字符!')
else:
    print('error!')