Python学习笔记_1_基础_3：列表、元组

一、列表

列表是Python 最常用的数据类型之一，通过列表可以对数据实现最方便的存储、修改等操作。

1、定义列表

names = ["Cz","Cao","Zhang","Hui","Yang"]
print(names)

2、元素访问：通过下标

>>> names = ["Cz","Cao","Zhang","Hui","Yang"]
>>> names[0]
'Cz'
>>> names[1]
'Cao'
>>> names[-1]
'Yang'

3、切片访问

>>> names = ["Cz","Cao","Zhang","Hui","Yang","Xiang","Xin"]
>>> names[1:3] #切片取值为[a,b)区间
['Cao', 'Zhang']
>>> names[:3]  #默认从头开始取值
['Cz', 'Cao', 'Zhang']
>>> names[-3:-1] #切片也能倒取
['Yang', 'Xiang']
>>> names[-3:]   #若倒取想获得最后一个值，只能用默认值
['Yang', 'Xiang', 'Xin']
>>> names[:4:2]  #步长为2，取值
['Cz', 'Zhang']

4、追加元素

>>> names = ["Cz","Cao","Zhang","Hui","Yang","Xiang","Xin"]
>>> names.append('New_person')
>>> print(names)
['Cz', 'Cao', 'Zhang', 'Hui', 'Yang', 'Xiang', 'Xin', 'New_person']

5、插入元素

>>> names = ["Cz","Cao","Zhang","Hui","Yang","Xiang","Xin"]
>>> names.insert(1,'New_person')
>>> names
['Cz', 'New_person', 'Cao', 'Zhang', 'Hui', 'Yang', 'Xiang', 'Xin']

6、修改元素

>>> names
['Cz', 'New_person', 'Cao', 'Zhang', 'Hui', 'Yang', 'Xiang', 'Xin']
>>> names[1] = 'Old_person'
>>> names
['Cz', 'Old_person', 'Cao', 'Zhang', 'Hui', 'Yang', 'Xiang', 'Xin']

7、删除元素

>>> names
['Cz', 'Old_person', 'Cao', 'Zhang', 'Hui', 'Yang', 'Xiang', 'Xin']
>>> del names[1]  #删除指定下标元素
>>> names
['Cz', 'Cao', 'Zhang', 'Hui', 'Yang', 'Xiang', 'Xin']
>>> names.remove('Xiang')  #删除指定元素
>>> names
['Cz', 'Cao', 'Zhang', 'Hui', 'Yang', 'Xin']
>>> names.pop()  #删除最后一个元素
'Xin'
>>> names
['Cz', 'Cao', 'Zhang', 'Hui', 'Yang']

8、获取下标

>>> names
['Cz', 'Cao', 'Zhang', 'Hui', 'Yang']
>>> names.index('Zhang')
2

返回元素第一次出现的下标。

9、统计元素出现次数

>>> names
['Cz', 'Cao', 'Zhang', 'Hui', 'Yang', 'Cz']
>>> names.count("Cz")
2

10、拓展：追加列表

num = [1,2,3]
>>> names.extend(num)
>>> names
['Cz', 'Cao', 'Zhang', 'Hui', 'Yang', 'Cz', 1, 2, 3]

11、列表排序、反转

>>> names
['Cz', 'Cao', 'Zhang', 'Hui', 'Yang', 'Cz', 1, 2, 3]
>>> names.sort()
Traceback (most recent call last):
  File "<pyshell#42>", line 1, in <module>
    names.sort()
TypeError: unorderable types: int() < str()
>>> names[-1] = '3'
>>> names[-2] = '2'
>>> names[-3] = '1'
>>> names.sort()
>>> names
['1', '2', '3', 'Cao', 'Cz', 'Cz', 'Hui', 'Yang', 'Zhang']
>>> #Python 3.x 里不同数据类型不能放在一起排序了
>>> names.reverse() #列表反转
>>> names
['Zhang', 'Yang', 'Hui', 'Cz', 'Cz', 'Cao', '3', '2', '1']

12、列表copy

>>> import copy
>>> copy1 = ["aa","bb",["ee","ff"],"cc","dd"]
>>> copy2 = copy.copy(copy1) #浅copy
>>> copy3 = copy.deepcopy(copy1) #深copy
>>> copy1[1] = "bbb"
>>> copy1[2][0] = "eee"
>>> copy1
['aa', 'bbb', ['eee', 'ff'], 'cc', 'dd']
>>> copy2
['aa', 'bb', ['eee', 'ff'], 'cc', 'dd']
>>> copy3
['aa', 'bb', ['ee', 'ff'], 'cc', 'dd']

Why?

Becase：学习引用后解释，目前记住浅copy时：copy1修改嵌套列表时，copy2同时被修改。

二、一个好玩但不太实用的列表copy例子

一对夫妻，维护同一个银行账户！虽然实际开发中绝对不会这么做。。。

可能还有其他应用场景，但是我没想到。（就连这个也是别处看到的。。。）

>>> import copy
>>> person = ['name',['saving','100']]
>>> p1 = person[:]
>>> p2 = person[:]
>>> p1
['name', ['saving', '100']]
>>> p2
['name', ['saving', '100']]
>>> p1[0] = 'cz'
>>> p2[0] = 'zhang'
>>> p1
['cz', ['saving', '100']]
>>> p2
['zhang', ['saving', '100']]
>>> p1[1][1] = 50    #其中一方花了50
>>> p1
['cz', ['saving', 50]]
>>> p2
['zhang', ['saving', 50]]

三、元组

元组（tuple）跟列表类似，也是存一组数据，只不是它一旦创建，便不能再修改，所以又叫只读列表。

有且仅有的两个方法，如下：

>>> names = ('cz','zhang','cao')
>>> names.count('cz')
1
>>> names.index('cz')
0

好，元组学完了。

四、练习

需求（该练习选自http://www.cnblogs.com/alex3714/articles/5717620.html）:

1. 启动程序后，让用户输入工资，然后打印商品列表
2. 允许用户根据商品编号购买商品
3. 用户选择商品后，检测余额是否够，够就直接扣款，不够就提醒 
4. 可随时退出，退出时，打印已购买商品和余额

salary = int(input('Please input you salary: '))

print('''This is a list of goods. Please choose!
Direct settlement after selection, do not return!
You can enter Q to leave!
Thank you!''')

commidity = [[1,'IPhone',6188],[2,'Honer',2188],[3,'Book',58],[4,'Computers',7888],[5,'Water',2],[6,'CPU_I7',3288]]
shopping_car = []

stat = '0'

while stat != 'Q':
    for comm in commidity:
        print(comm[0],'  ',comm[1],'  ',comm[2])

    stat = input('Please input you selection: ')
    
    if stat == 'Q':
        break

    if salary >= commidity[int(stat)-1][2]:
        shopping_car.append(commidity[int(stat)-1])
        salary = salary-commidity[int(stat)-1][2]
        print('Choose success！')

    if salary < commidity[int(stat)-1][2]:
        print('Sorry, your credit is running low!')

print('''Your balance is：{_salary}.
You have purchased the following commodities:'''.format(_salary=salary))
for shop in shopping_car:
    print(shop[0],'  ',shop[1],'  ',shop[2])

 

#较友好，判断输入是否正确
print('''This is a list of goods. Please choose!
Direct settlement after selection, do not return!
You can enter Q to leave!
Thank you!''')


commidity = [
    ['IPhone',6188],['Honer',2188],['Book',58],['Computers',7888],['Water',2],['CPU_I7',3288]
]
shopping_car = []


salary = input('Please input you salary: ')
if salary.isdigit():
    salary = int(salary)
    while True:
        for index,comm in enumerate(commidity):
            #print(commidity.index(comm),comm)
            print(index,comm)

        chioce = input('Please input you selection: ')

        if chioce.isdigit():
            chioce = int(chioce)
            if chioce < len(commidity) and chioce>=0:
                comm_p = commidity[chioce]
                if comm_p[1] <= salary:
                    shopping_car.append(comm_p)
                    salary -= comm_p[1]
                    print('Added %s into shopping cart.your current balance is \033[31;1m%s\033[0m'%(comm_p,salary))
                else:
                    print('\033[41;1m余额不足，只有[%s],买个毛线!\033[0m'%(salary))
            else:
                print('commidity code [%s] is not exists!'%salary)
        elif chioce == 'Q':
            print('-------------shopping list------------')
            for p in shopping_car:
                print(p)
            print('Your current balance:%s'%salary)
            exit()
        else:
            print('invalid option!')