python学习之路–python基础
- 2020 年 1 月 19 日
- 笔记
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 >>>
