Python 入门教程 9 ---- A Day at the Supermarket

第一节

1 介绍了for循环的用法

for variable in values:

statement

2 for循环打印出列表的每一项

for item in [1 , 2 , 3]:

print item

那么将打印出1，2，3

3 练习：使用for循环，把列表中的每一项打印出来

shopping_list = ["banana", "orange", "apple"]stock = { "banana": 6,    "apple": 0,    "orange": 32,    "pear": 15}    prices = { "banana": 4,    "apple": 2,    "orange": 1.5,    "pear": 3}# Write your code below!def compute_bill(food):    sum = 0    for str in food:        if(stock[str] > 0):           sum = sum + prices[str]           stock[str] = stock[str]-1    return sum