Python学习笔记文件操作list列表操作

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names =  ["cat","rat","lion","terger","cow","hen",'#$%^&','NIHASO','你好']

names = []

以上都是列表，使用[]对变量赋值就是列表

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从左到右下标是从0开始的，第一个是0

从右到左下标是从-1开始的，第一个是-1 

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1、列表的取值

（1）打印列表的所有内容

names = ["cat","rat","lion","terger","cow","hen",'#$%^&','NIHASO','你好']
print(names)#取所有值

　　运行结果：

（2）根据下标从左到右打印前4个值

names = ["cat","rat","lion","terger","cow","hen",'#$%^&','NIHASO','你好']

print(names[0:4])#取前四个，根据下标取值时，4本身不会被取出
print(names[:4])

　　运行结果：根据运行结果可看出，以上两种方法得到的结果是相同的

（3）根据下标打印最后4个值

names = ["cat","rat","lion","terger","cow","hen",'#$%^&','NIHASO','你好']

print(names[-5:-1])#取后四个，根据倒叙取值时，-1本身不会被取出
print(names[-4:])#从-4到-1全部取出

　　运行结果：

2、列表的增加

（1）append()函数，此函数的作用是在列表的最后面追加要写入的内容

names = ["cat","rat","lion","cow","hen"]

names.append("bat")#追加写入 在列表最后添加一个新的
print(names)

　　运行结果：

（2）insert()函数，此函数可指定插入的位置

names = ["cat","rat","lion","cow","hen"]

names.insert(1,"bat")#追加写入 在列表最后添加一个新的
print(names)

　　运行结果：

3、列表的删除

（1）remove()函数，此函数可指定要删除的内容

names = ["cat","rat","lion","cow","hen"]

names.remove("rat")#根据名字删除
print(names)

　　运行结果：

（2）del()函数，此函数可指定要删除的位置

names = ["cat","rat","lion","cow","hen"]

del names[0:2]#根据下标删除内容
print(names)

　　运行结果：

4、列表的改变

names = ["cat","rat","lion","cow","hen"]

names[0] = 'Mao'
print(names)

　　运行结果：

5、统计列表中重复内容

names = ["cat","cat","cat","lion","cow","hen"]

print(names.count('cat'))

　　运行结果：