【Python之旅】第二篇（三）：基于列表处理的购物清单程序
1.基本需求
编写一个购物小程序，要求实现如下功能：
（1）让用户输入工资；
（2）输出购物菜单及产品价格；
（3）计算用户是否可支付；
（4）输出用户剩余的钱，问用户是否继续购物，如果选择继续，则继续进行，否则退出程序；
（5）若钱不够，输出用户还需要工作多久才能买得起（这里暂不实现此功能）。
2.实现基本思路
基本思路可如下所示：
在编写程序的时候即以该思路为主线，具体细节下面再提及。
3.实现细节
基于友好用户界面的原则，实现的细节可总结如下：
（1）用户输入工资时，如果输入的是非数字或没有输入，会有提示再次输入，而不会异常退出；
（2）用户输入购买物品时，如果输入的是非商品索引或非quit退出时，会有提示再次输入，而不会异常退出；
（3）每添加商品到购物列表后，会提示用户当前所剩余的money；
（4）用户选择退出时，会打印用户的购物清单，同时输出用户剩余的money；
（5）总的原则是，程序在执行过程中不会有异常情况出现，即使用户输入非法字符。
4.实现代码与注释
基于上述需求的实现代码如下：
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#!/usr/bin/env pythonimport sys
market = [ ['Xiaomi Phone', 2400],
['Iphone', 6000],
['Computer', 3800],
['Ipad', 1800],
['Core Python', 69],
['Router', 109]
]shop_list = [] #The shopping list of the buyer.while True:
salary = raw_input('Please input your salary per month:').strip()
if not salary.isdigit():
print 'Please enter your salary.'
continue
salary = int(salary)
print "Welcome to our market!You can buy something cool here, or you can enter 'quit' to left.\n"
break
#Upon:input the salary per month.输入工资同时避免异常情况。while True:
print 'The goods we serve are as follow:'
for goods in market:
print market.index(goods),goods[0],goods[1]
#Upon:print the goods list.
choice = raw_input('What do you want to buy?')
if choice == 'quit': #'quit' system
print '\nYour shopping list are as follow:'
for goods in shop_list:
print goods[0],goods[1]
print 'Now you have %d left.' % (salary)
sys.exit('Goodbye!')
elif len(choice) == 0: #'enter' system
continue
#实际上'luanma' system和'enter' system可以只用前者进行替代，这里只是想输出不同提示而已。
（即输入乱码时会提示，输入enter时不进行提示。） if not choice.isdigit(): #'luanma' system，即如果用户输入非数字时，会有提示
print 'Please input the right choice.(Number to buy things and quit to quit.)\n'
continue
#Upon: 'quit' system , 'enter' system and 'luanma' handle system.
choice = int(choice)
if choice >= len(market):
print 'Could not find the item, try again!\n'
continue pri = market[choice]
#Upon:To check if the number is legal.确认输入的数字是否在合法范围内
pri = market[choice]
if pri[1] <= salary:
salary = salary - pri[1] #The remaining money.
shop_list.append(pri) #Adding the goods to the list.
print 'You have added %s to your shopping list, and you have %d left.\n' % (pri[0], salary)
else:
print '''You have %d left.
You can not afford to buy %s, but you can try to buy other things.\n''' % (salary, pri[0])
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因为灵活用了列表作处理，所以相对来说代码不会太复杂。
4.测试
·对输入过程中可能出现的各种情况和说明如下：
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[email protected]:/mnt/hgfs/Python/day2$ python myshop.py Please input your salary per month:Please enter your salary. ===>直接输入'Enter'时会有提示
Please input your salary per month:klkdfPlease enter your salary. ===>输入乱码时也会有提示Please input your salary per month:10000
Welcome to our market!You can buy something cool here, or you can enter 'quit' to left.
The goods we serve are as follow: ===>先打印了一个商品菜单
0 Xiaomi Phone 2400
1 Iphone 6000
2 Computer 3800
3 Ipad 1800
4 Core Python 69
5 Router 109
What do you want to buy?0 ===>正确输入商品索引号，会提示当前用户购物信息
You have added Xiaomi Phone to your shopping list, and you have 7600 left.
The goods we serve are as follow:
0 Xiaomi Phone 2400
1 Iphone 6000
2 Computer 3800
3 Ipad 1800
4 Core Python 69
5 Router 109
What do you want to buy? ===>只输入'Enter'时，不会有提示输出，但会再次打印商品菜单
The goods we serve are as follow:
0 Xiaomi Phone 2400
1 Iphone 6000
2 Computer 3800
3 Ipad 1800
4 Core Python 69
5 Router 109
What do you want to buy?3
You have added Ipad to your shopping list, and you have 5800 left.
The goods we serve are as follow:
0 Xiaomi Phone 2400
1 Iphone 6000
2 Computer 3800
3 Ipad 1800
4 Core Python 69
5 Router 109
What do you want to buy?eqwer ===>输入乱码时，会有提示，并接受再次输入
Please input the right choice.(Number to buy things and quit to quit.)
The goods we serve are as follow:
0 Xiaomi Phone 2400
1 Iphone 6000
2 Computer 3800
3 Ipad 1800
4 Core Python 69
5 Router 109
What do you want to buy?9 ===>输入不在合法范围内的数字时，也会有提示
Could not find the item, try again!
The goods we serve are as follow:
0 Xiaomi Phone 2400
1 Iphone 6000
2 Computer 3800
3 Ipad 1800
4 Core Python 69
5 Router 109
What do you want to buy?quit ===>正常退出，会打印用户总的购物清单信息
Your shopping list are as follow:
Xiaomi Phone 2400
Ipad 1800
Now you have 5800 left.
Goodbye! |
相对来说，用户界面还是比较友好的，因为不会有太大的异常情况出现，同时也实现了基本的需求。