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

arongsoft

　　

　　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
　　

names = ["Adam","Alex","Mariah","Martine","Columbus"]
# use for loop
for str in names:
print str
　　第二节
　　  1 介绍了我们可以使用for循环打印出字典中的每一个key
　　  2 比如这个例子，我们可以打印出key为foo的value值为bar
　　

# A simple dictionary
d = {"foo" : "bar"}
for key in d:
# prints "bar"
print d[key]



   3 练习：打印出字典webster的所有key对应的value
　　

webster = {
"Aardvark" : "A star of a popular children's cartoon show.",
"Baa" : "The sound a goat makes.",
"Carpet": "Goes on the floor.",
"Dab": "A small amount."
}
# Add your code below!
for key in webster:
print webster[key]
　　第三节
　　  1 介绍了for里面我们可以添加if/else语句来判断
　　  2 比如
　　

for item in numbers:
if condition:
# Do something

  3 练习：只输出列表中的7个数
　　

a = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]
for num in a:
if(a < 7):
print a


　　第四节
　　  1 介绍了在函数里面使用for循环
　　  2 练习
　　    1 写一个函数名为fizz_count，参数为列表x
　　    2 函数返回列表中值为"fizz"的个数
　　

# Write your function below!
def fizz_count(x):
sum = 0
for str in x:
if(str == "fizz"):
sum = sum+1
return sum


　　第五节
　　  1 练习：把以下的对应关系建立成字典prices

# the key and values
"banana": 4
"apple": 2
"orange": 1.5
"pear": 3
# you code here
prices = {}
prices["banana"] = 4
prices["apple"] = 2
prices["orange"] = 1.5
prices["pear"] = 3


　　第六节
　　  1 练习：按照以下的格式输出
　　

item
price: x
stock: x
# such as
apple
price: 2
stock: 0
　　

# the first dictionary
prices = {}
prices["banana"] = 4
prices["apple"] = 2
prices["orange"] = 1.5
prices["pear"] = 3
# the second dictionary
stock = {}
stock["banana"] = 6
stock["apple"] = 0
stock["orange"] = 32
stock["pear"] = 15
# you code here
for key in prices:
print key
print "price: "+prices[key]
print "stock: "+stock[key]



第七节　　  1 练习
　　    1 创建一个列表名叫groceries，有三个值分别为"banana","orange", "apple"
　　    2 写一个函数名叫compute_bill，参数是列表food
　　    3 利用循环计算出food中所有物品的总价格
　　

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:
sum = sum + prices[str]
return sum


　　第八节
　　  1 练习
　　    1 创建一个列表名叫groceries，有三个值分别为"banana","orange", "apple"
　　    2 写一个函数名叫compute_bill，参数是列表food
　　    3 利用循环计算出food中所有物品的总价格，但是我们在求价格的时候我们一个先判断在stock字典中对应的值是否大于0，如果是的话才进行求和并且把stock对应的value值减一


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