Python学习随笔_2_基础：列表元组

Posted 2021-01-01 104cz

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

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

2、元素访问：通过下标

1 >>> names = ["Cz","Cao","Zhang","Hui","Yang"]
2 >>> names[0]
3 ‘Cz‘
4 >>> names[1]
5 ‘Cao‘
6 >>> names[-1]
7 ‘Yang‘

3、切片访问

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

4、追加元素

1 >>> names = ["Cz","Cao","Zhang","Hui","Yang","Xiang","Xin"]
2 >>> names.append(‘New_person‘)
3 >>> print(names)
4 [‘Cz‘, ‘Cao‘, ‘Zhang‘, ‘Hui‘, ‘Yang‘, ‘Xiang‘, ‘Xin‘, ‘New_person‘]

5、插入元素

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

6、修改元素

1 >>> names
2 [‘Cz‘, ‘New_person‘, ‘Cao‘, ‘Zhang‘, ‘Hui‘, ‘Yang‘, ‘Xiang‘, ‘Xin‘]
3 >>> names[1] = ‘Old_person‘
4 >>> names
5 [‘Cz‘, ‘Old_person‘, ‘Cao‘, ‘Zhang‘, ‘Hui‘, ‘Yang‘, ‘Xiang‘, ‘Xin‘]

7、删除元素

 1 >>> names
 2 [‘Cz‘, ‘Old_person‘, ‘Cao‘, ‘Zhang‘, ‘Hui‘, ‘Yang‘, ‘Xiang‘, ‘Xin‘]
 3 >>> del names[1]  #删除指定下标元素
 4 >>> names
 5 [‘Cz‘, ‘Cao‘, ‘Zhang‘, ‘Hui‘, ‘Yang‘, ‘Xiang‘, ‘Xin‘]
 6 >>> names.remove(‘Xiang‘)  #删除指定元素
 7 >>> names
 8 [‘Cz‘, ‘Cao‘, ‘Zhang‘, ‘Hui‘, ‘Yang‘, ‘Xin‘]
 9 >>> names.pop()  #删除最后一个元素
10 ‘Xin‘
11 >>> names
12 [‘Cz‘, ‘Cao‘, ‘Zhang‘, ‘Hui‘, ‘Yang‘]

8、获取下标

1 >>> names
2 [‘Cz‘, ‘Cao‘, ‘Zhang‘, ‘Hui‘, ‘Yang‘]
3 >>> names.index(‘Zhang‘)
4 2

返回元素第一次出现的下标。

9、统计元素出现次数

1 >>> names
2 [‘Cz‘, ‘Cao‘, ‘Zhang‘, ‘Hui‘, ‘Yang‘, ‘Cz‘]
3 >>> names.count("Cz")
4 2

10、拓展：追加列表

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

11、列表排序、反转

 1 >>> names
 2 [‘Cz‘, ‘Cao‘, ‘Zhang‘, ‘Hui‘, ‘Yang‘, ‘Cz‘, 1, 2, 3]
 3 >>> names.sort()
 4 Traceback (most recent call last):
 5   File "<pyshell#42>", line 1, in <module>
 6     names.sort()
 7 TypeError: unorderable types: int() < str()
 8 >>> names[-1] = ‘3‘
 9 >>> names[-2] = ‘2‘
10 >>> names[-3] = ‘1‘
11 >>> names.sort()
12 >>> names
13 [‘1‘, ‘2‘, ‘3‘, ‘Cao‘, ‘Cz‘, ‘Cz‘, ‘Hui‘, ‘Yang‘, ‘Zhang‘]
14 >>> #Python 3.x 里不同数据类型不能放在一起排序了
15 >>> names.reverse() #列表反转
16 >>> names
17 [‘Zhang‘, ‘Yang‘, ‘Hui‘, ‘Cz‘, ‘Cz‘, ‘Cao‘, ‘3‘, ‘2‘, ‘1‘]

View Code

12、列表copy

 1 >>> import copy
 2 >>> copy1 = ["aa","bb",["ee","ff"],"cc","dd"]
 3 >>> copy2 = copy.copy(copy1) #浅copy
 4 >>> copy3 = copy.deepcopy(copy1) #深copy
 5 >>> copy1[1] = "bbb"
 6 >>> copy1[2][0] = "eee"
 7 >>> copy1
 8 [‘aa‘, ‘bbb‘, [‘eee‘, ‘ff‘], ‘cc‘, ‘dd‘]
 9 >>> copy2
10 [‘aa‘, ‘bb‘, [‘eee‘, ‘ff‘], ‘cc‘, ‘dd‘]
11 >>> copy3
12 [‘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。。。）

 1 >>> import copy
 2 >>> person = [‘name‘,[‘saving‘,‘100‘]]
 3 >>> p1 = person[:]
 4 >>> p2 = person[:]
 5 >>> p1
 6 [‘name‘, [‘saving‘, ‘100‘]]
 7 >>> p2
 8 [‘name‘, [‘saving‘, ‘100‘]]
 9 >>> p1[0] = ‘cz‘
10 >>> p2[0] = ‘zhang‘
11 >>> p1
12 [‘cz‘, [‘saving‘, ‘100‘]]
13 >>> p2
14 [‘zhang‘, [‘saving‘, ‘100‘]]
15 >>> p1[1][1] = 50    #其中一方花了50
16 >>> p1
17 [‘cz‘, [‘saving‘, 50]]
18 >>> p2
19 [‘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：

1 >>> names = (‘cz‘,‘zhang‘,‘cao‘)
2 >>> names.count(‘cz‘)
3 1
4 >>> names.index(‘cz‘)
5 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

 1 salary = int(input(‘Please input you salary: ‘))
 2 
 3 print(‘‘‘This is a list of goods. Please choose!
 4 Direct settlement after selection, do not return!
 5 You can enter Q to leave!
 6 Thank you!‘‘‘)
 7 
 8 commidity = [[1,‘IPhone‘,6188],[2,‘Honer‘,2188],[3,‘Book‘,58],[4,‘Computers‘,7888],[5,‘Water‘,2],[6,‘CPU_I7‘,3288]]
 9 shopping_car = []
10 
11 stat = ‘0‘
12 
13 while stat != ‘Q‘:
14     for comm in commidity:
15         print(comm[0],‘  ‘,comm[1],‘  ‘,comm[2])
16 
17     stat = input(‘Please input you selection: ‘)
18     
19     if stat == ‘Q‘:
20         break
21 
22     if salary >= commidity[int(stat)-1][2]:
23         shopping_car.append(commidity[int(stat)-1])
24         salary = salary-commidity[int(stat)-1][2]
25         print(‘Choose success！‘)
26 
27     if salary < commidity[int(stat)-1][2]:
28         print(‘Sorry, your credit is running low!‘)
29 
30 print(‘‘‘Your balance is：{_salary}.
31 You have purchased the following commodities:‘‘‘.format(_salary=salary))
32 for shop in shopping_car:
33     print(shop[0],‘  ‘,shop[1],‘  ‘,shop[2])

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