python学习之路--python基础之列表操作

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

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

 >>> names[0]
 'ZhangSan'
 >>> names[2]
 'WangWu'
 >>> names[-1]
 'WangWu'
 >>> names[-2]
 'LiSi'
 >>>

切片操作

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

追加操作：在列表最后追加元素列表

 >>> names=['ZhangSan','LiSi','WangWu']
 >>> names.append("我是新人")
 >>> names
 ['ZhangSan', 'LiSi', 'WangWu', '我是新人']
 >>>

插入操作

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

修改操作

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

删除操作

 >>> names=['ZhangSan','LiSi','WangWu','ZhaoLiu','Tony','Tom','LiLei']
 >>> del names[2]  #删除下标为2的元素，即WangWu
 >>> names
 ['ZhangSan', 'LiSi', 'ZhaoLiu', 'Tony', 'Tom', 'LiLei']
 >>> del names[4]  #删除下标为4的元素，即Tom
 >>> names
 ['ZhangSan', 'LiSi', 'ZhaoLiu', 'Tony', 'LiLei']
 >>> names.remove("Tony")  #删除指定的元素Tony
 >>> names
 ['ZhangSan', 'LiSi', 'ZhaoLiu', 'LiLei']
 >>> names.pop()  #删除最后一个元素
 'LiLei'
 >>> names
 ['ZhangSan', 'LiSi', 'ZhaoLiu']
 >>>

扩展操作

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

统计列表中相同元素的个数

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

排序和翻转：优先级   特殊符号>数字>大写>小写

 >>> names=['ZhangSan', 'LiSi', 'ZhaoLiu','LiSi',1, 2, 3]
 >>> names.sort()
 Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
 TypeError: unorderable types: int() < str()  #在python3里面不同数据类型不能在一起排序
 >>>
 >>> names[-1]=''
 >>> names[-2]=''
 >>> names[-3]=''
 >>> names
 ['LiSi', 'LiSi', 'ZhangSan', 'ZhaoLiu', '', '', '']
 >>> names.sort()  #将列表排序
 >>> names
 ['', '', '', 'LiSi', 'LiSi', 'ZhangSan', 'ZhaoLiu']
 >>> names.reverse()  #将列表反转
 >>> names
 ['ZhaoLiu', 'ZhangSan', 'LiSi', 'LiSi', '', '', '']
 >>>

获取下标

 >>> names=['ZhaoLiu', 'ZhangSan', 'LiSi', 'LiSi', '', '', '']
 >>> 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
 2
 >>> names.index('')
 4
 >>>

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。

 >>> names=['ZhaoLiu', 'ZhangSan',['lilei','luxi'], 'LiSi','', '', '']
 >>> name_copy=names.copy()  #只是浅复制
 >>> names
 ['ZhaoLiu', 'ZhangSan', ['lilei', 'luxi'], 'LiSi', '', '', '']
 >>> name_copy
 ['ZhaoLiu', 'ZhangSan', ['lilei', 'luxi'], 'LiSi', '', '', '']
 >>> names[1]="张三"   #只改变names里面的值，name_copy里面的不变
 >>> names
 ['ZhaoLiu', '张三', ['lilei', 'luxi'], 'LiSi', '', '', '']
 >>> name_copy
 ['ZhaoLiu', 'ZhangSan', ['lilei', 'luxi'], 'LiSi', '', '', '']
 >>> names[2][0]="LILEI"  #names和name_copy里面的值都改变
 >>> names
 ['ZhaoLiu', '张三', ['LILEI', 'luxi'], 'LiSi', '', '', '']
 >>> name_copy
 ['ZhaoLiu', 'ZhangSan', ['LILEI', 'luxi'], 'LiSi', '', '', '']
 >>> name_copy[2][1]='露西'
 >>> names
 ['ZhaoLiu', '张三', ['LILEI', '露西'], 'LiSi', '', '', '']
 >>> name_copy
 ['ZhaoLiu', 'ZhangSan', ['LILEI', '露西'], 'LiSi', '', '', '']

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。

 #Author:Zhang XuLin
 import copy
 names=['ZhaoLiu', 'ZhangSan',['lilei','luxi'], 'LiSi','', '', '']
 name_copy=copy.deepcopy(names)
 print(names)
 print(name_copy)
 print("========================")
 #['ZhaoLiu', 'ZhangSan', ['lilei', 'luxi'], 'LiSi', '3', '2', '1']
 #['ZhaoLiu', 'ZhangSan', ['lilei', 'luxi'], 'LiSi', '3', '2', '1']
 #========================
 names[1]="张三"
 print(names)
 print(name_copy)
 print("========================")
 #['ZhaoLiu', '张三', ['lilei', 'luxi'], 'LiSi', '3', '2', '1']
 #['ZhaoLiu', 'ZhangSan', ['lilei', 'luxi'], 'LiSi', '3', '2', '1']
 #========================

 names[2][0]="LILEI"
 print(names)
 print(name_copy)
 print("************************************")
 #['ZhaoLiu', '张三', ['LILEI', 'luxi'], 'LiSi', '3', '2', '1']
 #['ZhaoLiu', 'ZhangSan', ['lilei', 'luxi'], 'LiSi', '3', '2', '1']
 #************************************

 name_copy[2][1]='露西'
 print(names)
 print(name_copy)

 #['ZhaoLiu', '张三', ['LILEI', 'luxi'], 'LiSi', '3', '2', '1']
 #['ZhaoLiu', 'ZhangSan', ['lilei', '露西'], 'LiSi', '3', '2', '1']

清空和删除列表

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