Python学习——A Day at the Supermarket小项目

前言

A Day at the Supermarket该项目用来回顾/强化之前学习Python的知识点。

1、Before We Begin

names = ["Adam","Alex","Mariah","Martine","Columbus"]for elements in names:    print elements

上述代码，使用for循环，将names这个list中的items逐个输出/打印出来——遍历。

2、This is Key！

对dictionary使用for循环，输出是无序的，即每次输出，“key/value对”的顺序是无序的。

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]

输出结果如下：

3、Control Flow and Looping

在循环中，有选择性地输出数据

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

4、Lists + Functions

函数可以将List作为其输入参数，进行下一步操作运算

任务：Write a function that counts how many times the string "fizz" appears in a list.

# Write your function below!def fizz_count(x):    count = 0    for item in x:        if item == "fizz":            count += 1    return countfizz_count(["fizz","cat","fizz"])

5、String Looping

字符串和list类似，其每个字符相当于元素，所以字符串也可以像list一样循环操作。

可参见下述代码：

for letter in "Codecademy":    print letter    # Empty lines to make the output prettyprintprintword = "Programming is fun!"for letter in word:    # Only print out the letter i    if letter == "i":        print letter

6、Your Own Store!

创建一个价格dictionary——prices

prices = {    "banana": 4,     "apple": 2,     "orange": 1.5,     "pear": 3}

7、Investing in Stock

创建一个库存dictionary——stock

stock = {    "banana": 6,    "apple": 0,    "orange": 32,    "pear": 15}

8、Keeping Track of the Produce

输出价格和库存信息

prices = {    "banana": 4,     "apple": 2,     "orange": 1.5,     "pear": 3}stock = {    "banana": 6,    "apple": 0,    "orange": 32,    "pear": 15}for key in prices:    print key    print "price: %s" % prices[key]    print "stock: %s" % stock[key]

9、Something of Value

将每种商品的总价格及所有商品的价格计算并打印出来

total = 0for key in prices:    print "prices: %s" % prices[key]*stock[key]    total += prices[key]*stock[key]print total

10、Shopping at  the Market

groceries = ["banana", "orange", "apple"]

11、Making a Purchase

计算自己选购商品的价格

def compute_bill(food):    total = 0    for item in food:            total += prices[item]            stock[item] -= 1    return total

12、Stocking Out

提示：If you're buying a banana, check if it's in stock (larger than zero). If it's in stock, add the cost of a banana to your bill. Finally, decrement the stock of bananas by one!

def compute_bill(food):    total = 0    for item in food:        if stock[item] > 0:            total += prices[item]            stock[item] -= 1    return total

13、Let's Check Out!

上述已经完成list、dictionary的创建

• ——Using for loops with lists and dictionaries
• ——Writing functions with loops, lists, and dictionaries
• ——Updating data in response to changes in the environment (for instance, decreasing the number of bananas in stock by 1 when you sell one).
• 完整代码如下：

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):    total = 0    for item in food:        if stock[item] > 0:            total += prices[item]            stock[item] -= 1    return total