python学习之路--python基础

本文主要介绍下python列表的的一些基本操作

列表是我们在Python编程中常用的数据类型之一，通过列表我们可以对数据实现最方便的存储、修改等操作。

定义列表

 1 names=['ZhangSan','LiSi','WangWu'] 

列表的访问：通过下表来访问列表中的元素，下标从0开始计数,还可以反着取，-1表示最后一个元素

1 >>> names[0]
2 'ZhangSan'
3 >>> names[2]
4 'WangWu'
5 >>> names[-1]
6 'WangWu'
7 >>> names[-2]
8 'LiSi'
9 >>>

切片操作

 1 >>> names=['ZhangSan','LiSi','WangWu','ZhaoLiu','Tom','Amy']
 2 >>> names[1:4]  #取下标1到4之间的数据元素，包括1，不包括4
 3 ['LiSi', 'WangWu', 'ZhaoLiu']
 4 >>> names[1:-1]  #取小标1到-1的值，不包括-1
 5 ['LiSi', 'WangWu', 'ZhaoLiu', 'Tom']
 6 >>> names[0:3]
 7 ['ZhangSan', 'LiSi', 'WangWu']
 8 >>> names[:3]  #如果是从头开始取，0可以忽略，跟上句结果一样
 9 ['ZhangSan', 'LiSi', 'WangWu']
10 >>> names[3:]  #如果想取最后一位，必须不能写-1
11 ['ZhaoLiu', 'Tom', 'Amy']
12 >>> names[3:-1]  #不包含-1
13 ['ZhaoLiu', 'Tom']
14 >>> names[0::2]  #2代表步长，每隔一个元素就取一个
15 ['ZhangSan', 'WangWu', 'Tom']
16 >>> names[::2]  #和上句效果一样
17 ['ZhangSan', 'WangWu', 'Tom']
18 >>>

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 追加操作：在列表最后追加元素列表

1 >>> names=['ZhangSan','LiSi','WangWu']
2 >>> names.append("我是新人")
3 >>> names
4 ['ZhangSan', 'LiSi', 'WangWu', '我是新人']
5 >>>

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插入操作

1 >>> names=['ZhangSan','LiSi','WangWu','Tony']
2 >>> names.insert(2,"Tom")  #在WangWu前面插入Tom
3 >>> names
4 ['ZhangSan', 'LiSi', 'Tom', 'WangWu', 'Tony']
5 >>> names.insert(4,"LuXi")  #在WangWu后面插入LuXi
6 >>> names
7 ['ZhangSan', 'LiSi', 'Tom', 'WangWu', 'LuXi', 'Tony']
8 >>>

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修改操作

1 >>> names=['ZhangSan','LiSi','WangWu','Tony']
2 >>> names[2]="John" ##将WangWu改成"John"
3 >>> names
4 ['ZhangSan', 'LiSi', 'John', 'Tony']
5 >>>

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删除操作

 1 >>> names=['ZhangSan','LiSi','WangWu','ZhaoLiu','Tony','Tom','LiLei']
 2 >>> del names[2]  #删除下标为2的元素，即WangWu
 3 >>> names
 4 ['ZhangSan', 'LiSi', 'ZhaoLiu', 'Tony', 'Tom', 'LiLei']
 5 >>> del names[4]  #删除下标为4的元素，即Tom
 6 >>> names
 7 ['ZhangSan', 'LiSi', 'ZhaoLiu', 'Tony', 'LiLei']
 8 >>> names.remove("Tony")  #删除指定的元素Tony
 9 >>> names
10 ['ZhangSan', 'LiSi', 'ZhaoLiu', 'LiLei']
11 >>> names.pop()  #删除最后一个元素
12 'LiLei'
13 >>> names
14 ['ZhangSan', 'LiSi', 'ZhaoLiu']
15 >>>

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扩展操作

1 >>> names=['ZhangSan', 'LiSi', 'ZhaoLiu']
2 >>> b=[1,2,3]
3 >>> names.extend(b)
4 >>> names
5 ['ZhangSan', 'LiSi', 'ZhaoLiu', 1, 2, 3]
6 >>>

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统计列表中相同元素的个数

1 >>> names=['ZhangSan', 'LiSi', 'ZhaoLiu','LiSi',1, 2, 3]
2 >>> names.count("LiSi")
3 2
4 >>>

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排序和翻转：优先级   特殊符号>数字>大写>小写

 1 >>> names=['ZhangSan', 'LiSi', 'ZhaoLiu','LiSi',1, 2, 3]
 2 >>> names.sort()
 3 Traceback (most recent call last):
 4   File "<stdin>", line 1, in <module>
 5 TypeError: unorderable types: int() < str()  #在python3里面不同数据类型不能在一起排序
 6 >>>
 7 >>> names[-1]='3'
 8 >>> names[-2]='2'
 9 >>> names[-3]='1'
10 >>> names
11 ['LiSi', 'LiSi', 'ZhangSan', 'ZhaoLiu', '1', '2', '3']
12 >>> names.sort()  #将列表排序
13 >>> names
14 ['1', '2', '3', 'LiSi', 'LiSi', 'ZhangSan', 'ZhaoLiu']
15 >>> names.reverse()  #将列表反转
16 >>> names
17 ['ZhaoLiu', 'ZhangSan', 'LiSi', 'LiSi', '3', '2', '1']
18 >>>

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获取下标

1 >>> names=['ZhaoLiu', 'ZhangSan', 'LiSi', 'LiSi', '3', '2', '1']
2 >>> names.index('LiSi')  #如果列表中有多个相同元素，只返回找到的第一个的下标
3 2
4 >>> names.index('3')
5 4
6 >>>

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浅拷贝copy():

浅复制并不会产生一个独立的对象单独存在，他只是将原有的数据块打上一个新标签，所以当其中一个标签被改变的时候，数据块就会发生变化，另一个标签也会随之改变。

 1 >>> names=['ZhaoLiu', 'ZhangSan',['lilei','luxi'], 'LiSi','3', '2', '1']
 2 >>> name_copy=names.copy()  #只是浅复制
 3 >>> names
 4 ['ZhaoLiu', 'ZhangSan', ['lilei', 'luxi'], 'LiSi', '3', '2', '1']
 5 >>> name_copy
 6 ['ZhaoLiu', 'ZhangSan', ['lilei', 'luxi'], 'LiSi', '3', '2', '1']
 7 >>> names[1]="张三"   #只改变names里面的值，name_copy里面的不变
 8 >>> names
 9 ['ZhaoLiu', '张三', ['lilei', 'luxi'], 'LiSi', '3', '2', '1']
10 >>> name_copy
11 ['ZhaoLiu', 'ZhangSan', ['lilei', 'luxi'], 'LiSi', '3', '2', '1']
12 >>> names[2][0]="LILEI"  #names和name_copy里面的值都改变
13 >>> names
14 ['ZhaoLiu', '张三', ['LILEI', 'luxi'], 'LiSi', '3', '2', '1']
15 >>> name_copy
16 ['ZhaoLiu', 'ZhangSan', ['LILEI', 'luxi'], 'LiSi', '3', '2', '1']
17 >>> name_copy[2][1]='露西'
18 >>> names
19 ['ZhaoLiu', '张三', ['LILEI', '露西'], 'LiSi', '3', '2', '1']
20 >>> name_copy
21 ['ZhaoLiu', 'ZhangSan', ['LILEI', '露西'], 'LiSi', '3', '2', '1']

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深复制deepcopy():

我们寻常意义的复制就是深复制，即将被复制对象完全再复制一遍作为独立的新个体单独存在。所以改变原有被复制对象不会对已经复制出来的新对象产生影响。

 1 #Author:Zhang XuLin
 2 import copy
 3 names=['ZhaoLiu', 'ZhangSan',['lilei','luxi'], 'LiSi','3', '2', '1']
 4 name_copy=copy.deepcopy(names)
 5 print(names)
 6 print(name_copy)
 7 print("========================")
 8 #['ZhaoLiu', 'ZhangSan', ['lilei', 'luxi'], 'LiSi', '3', '2', '1']
 9 #['ZhaoLiu', 'ZhangSan', ['lilei', 'luxi'], 'LiSi', '3', '2', '1']
10 #========================
11 names[1]="张三"
12 print(names)
13 print(name_copy)
14 print("========================")
15 #['ZhaoLiu', '张三', ['lilei', 'luxi'], 'LiSi', '3', '2', '1']
16 #['ZhaoLiu', 'ZhangSan', ['lilei', 'luxi'], 'LiSi', '3', '2', '1']
17 #========================
18 
19 names[2][0]="LILEI"
20 print(names)
21 print(name_copy)
22 print("************************************")
23 #['ZhaoLiu', '张三', ['LILEI', 'luxi'], 'LiSi', '3', '2', '1']
24 #['ZhaoLiu', 'ZhangSan', ['lilei', 'luxi'], 'LiSi', '3', '2', '1']
25 #************************************
26 
27 name_copy[2][1]='露西'
28 print(names)
29 print(name_copy)
30 
31 #['ZhaoLiu', '张三', ['LILEI', 'luxi'], 'LiSi', '3', '2', '1']
32 #['ZhaoLiu', 'ZhangSan', ['lilei', '露西'], 'LiSi', '3', '2', '1']

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 清空和删除列表

 1 >>> names=['ZhaoLiu', 'ZhangSan',['lilei','luxi'], 'LiSi','3', '2', '1']
 2 >>> names.clear()  #将列表清空
 3 >>> names
 4 []
 5 >>> del names  #将列表删除
 6 >>> names
 7 Traceback (most recent call last):
 8   File "<stdin>", line 1, in <module>
 9 NameError: name 'names' is not defined
10 >>>