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Stroke list in python (bottom)
2022-01-30 23:35:42 【Lei Xuewei】
「 This is my participation 11 The fourth of the yuegengwen challenge 2 God , Check out the activity details ：2021 One last more challenge 」
ceremonial Python Column No 27 piece , Classmate, stop , Don't miss this from 0 The beginning of the article ！
The first part is the comparison of the Academic Committee tuple The operation of the article is listed one by one list Corresponding operation of list data .
This time we continue to list After reading other operations of .
The school committee mentioned earlier tuple（ Tuples ） It's a series of welded carriages ,list Support element editing , Obviously much more flexible .
Let's first look at the delete operation ,python Medium list It supports 3 Delete element in .
Suppose we define a list object list_obj, Then we can do any of the following , Delete the element .
del list_obj[ Subscript ] list_obj.remove( An element value ） list_obj.pop( Subscript ） # Return element value Copy code
good , Let's look at the complete code below ：
#!/usr/bin/env python # -*- coding: utf-8 -*- # @Time : 2021/10/31 10:36 Afternoon # @Author : LeiXueWei # @CSDN/Juejin/Wechat: Lei Xuewei # @XueWeiTag: CodingDemo # @File : list_demo4.py # @Project : hello # Delete list elements mylist = [1, 0, 2, 4, " Lei Xuewei "] print("mylist:", mylist) del mylist print("after remove first element, mylist:", mylist) mylist.remove(" Lei Xuewei ") print("after remove first element, mylist:", mylist) removed_value = mylist.pop(1) # Remove and return the element value print("after remove first element, mylist:", mylist) print("removed value:", removed_value) Copy code
The effect is as follows ：
One thing in particular to note ： Delete element cannot exceed list Subscript range , Otherwise, the report will be wrong ！
In addition to deleting ,list How to add / What about extension elements ？
Not to mention the modified ,list It also supports locating and finding elements , Let's see .
list_obj.index( An element value ） # Locate the first matching subscript by an element value , from 0 The location starts to look for . Copy code
hypothesis list_obj = [3, 2, 1] that list_obj.index(2) What is it ？
The answer is ：1.
good , Let's go on to insert new elements .
# python Medium list Support the following two ways to append elements list_obj.insert( Specify subscript , Elements ） list_obj.append( Elements ） # The last element Copy code
Then add multiple at one time , Or directly expand a list to an existing list ？
We found it extend function , Use list_obj.extend( Supplementary list ） Can handle list_obj Directly expanded , The effect is to append the elements of the supplementary list to the end in turn .
Say so many operations , Let's copy and run the following code directly to see ：
#!/usr/bin/env python # -*- coding: utf-8 -*- # @Time : 2021/10/31 10:36 Afternoon # @Author : LeiXueWei # @CSDN/Juejin/Wechat: Lei Xuewei # @XueWeiTag: CodingDemo # @File : list_demo5.py # @Project : hello # Other functions of the list mylist = [6, 6, 6] print("mylist:", mylist) mylist.append(" Lei Xuewei ") print("mylist:", mylist) print(" How many lists 6？:", mylist.count(6)) print(" first 6 Location subscript of ？:", mylist.index(6)) mylist.insert(2, 1024) print(" first 1024 Location subscript of ？:", mylist.index(1024)) last = mylist.pop() # The delete operation has been described earlier , Here are a few examples . print(" The last element is ：",last) print("mylist:", mylist) # Directly append a new list mylist.extend(mylist) # amount to mylist = mylist * 2 print("mylist:", mylist) mylist.extend([' Continuous learning ', ' Continuous development ']) print("mylist:", mylist) Copy code
This is the effect of code running ：
It's very simple , Let's continue to look at the sorting of list elements
All the above are editing operations ,list You can also arrange data , According to It must be logical Arrange in order .
list Provides a sort Functions and reverse function .
Let's start with the simple ,reverse The function is equivalent to turning the whole train directly . That is to say list:[1,2,3] after reverse After the function , Turned into [3,2,1].
sort More elastic , The default installation element is （ Such as digital , Digital string ）, It also supports the introduction of a lambda function , Specifies the sort logic .
By default, the above function will sort an array composed of numbers by the size of their face value
#!/usr/bin/env python # -*- coding: utf-8 -*- # @Time : 2021/10/31 10:36 Afternoon # @Author : LeiXueWei # @CSDN/Juejin/Wechat: Lei Xuewei # @XueWeiTag: CodingDemo # @File : list_demo6.py # @Project : hello # Other functions of the list mylist = [2, 3, 1] #mylist = ["2", "3", "1"] mylist.sort() print("mylist:", mylist) mylist.extend([' Continuous learning ', ' Continuous development ']) print("mylist:", mylist) mylist.sort(key=lambda e: len(str(e)), reverse=True) print("sorted mylist:", mylist) mylist.reverse() print("reversed mylist:", mylist) Copy code
The effect is as follows , Readers can take a closer look at whether it is as the school committee said .
Particular attention ： The above example code of the school committee also shows , If the elements in a list are not of the same type （ It's all numbers , Are all strings or some type ）, Developers must implement a lambda Function gives sort Function as a reference to sort .
list There are many functions , Operate on elements （ add to / Delete / location ） Waiting is very convenient .
And it can be easily expanded , Sort , Reverse order, etc. , This makes list It is widely used , Every study python Be sure to type more code , Master skillfully .
by the way , like Python Friend, , Please pay attention to Python Basic column or Python From getting started to mastering the big column
Continuous learning and continuous development , I'm Lei Xuewei ！
Programming is fun , The key is to understand the technology thoroughly .
Welcome to wechat , Like support collection !
author[Lei Xuewei],Please bring the original link to reprint, thank you.
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