Summary of the usage of * args and * * kwargs in Python

sxxbxh 2020-11-16 14:33:40
summary usage args kwargs python

For the most part Python beginners ,*args and **kwargs These two magic variables take a lot of time to explain . So what are they ? When to use them ? We need to figure out these problems , First of all, you need to understand , Actually, it doesn't have to be written as *args and **kwargs. It's just in front of the variable *( asterisk ) Is a must . Let's take a look at Python in *args and **kwargs Let's summarize the usage of .

1、*args Usage of

*args and **kwargs Mainly used for function definition . You can pass an indefinite number of arguments to a function . Indefinite here means that you don't know in advance how many parameters the user will pass to you , So use these two keywords in this scenario .*args Is used to send a variable number of arguments of a non key value pair to a function . Here's an example to help you understand this concept :

def test_ var_ args(f_ _arg, *argv) :

print ("first normal arg:", f_ arg)

for arg in argv :

print ( " another arg through *argv:", arg)

test_ var_ args(' yasoob',' python',' eggs' ,' test' )

This produces the following output :

first normal arg: yasoob

another arg through *argv: python

another arg through *argv: eggs

another arg through *argv : test

2、**kwargs Usage of

**kwargs Allows you to set variable length key value pairs , Pass as an argument to a function . If you want to handle named arguments in a function , You should use **kwargs. Here's an example to get you started :

def greet_ me (**kwargs) :

for key, value in kwargs. items () :

print("{0} == {1}". format (key, value) )

>>> greet me (name="yasoob")

name == yasoob

Now you can see how we're in a function , Processed a key value pair parameter . This is it. **kwargs The basis of , And you can see how effective it is .

3、 Use *args and **kwargs To call a function

Suppose you have such a small function :

def test_ _args_ kwargs (arg1, arg2, arg3) :

print ("arg1:",arg1)

print("arg2:", arg2) .

print ("arg3:",arg3)

You can use *args or ** kwargs To pass parameters to this small function . Here's how to do it :

# Mouth first makes mouth *args .

>>> args = ("two", 3, 5)

>>> test_ args_ kwargs (*args)

arg1: twO

arg2: 3

arg3: 5

# Now let's talk **kwargs:

>>> kwargs = {"arg3": 3, "arg2": "two", "arg1": 5}

>>> test_ args_ kwargs (** kwargs)

arg1: 5

arg2: two

arg3: 3

4、 Standard parameters and *args、**kwargs In the order of use

So if you want to use all three parameters in a function at the same time , This is the order :

some_ func(fargs, *args, **kwargs)

5、 When to use Python in *args and **kwargs?

It really depends on your needs . The most common use case is when writing function decorators . In addition, it can also be used to make monkey patches . Monkey patch means when the program is running ,(runtime) Modify some code . For example , You have a class , There's a man in it called get_ info The function of will call a API And return the corresponding data . If we want to test it , You can put API Call to replace with some test data . for example :

import someclass

def get_ info(self, *args) :

return "Test data"

someclass.get_ info = get_ info

That's all Python in *args and **kwargs To sum up the usage of , Have you solved all your doubts ? Xinxiang treatment of infertility how much money : Zhengzhou Tongji Hospital is good : Zhengzhou Tongji Infertility Research Institute :


  1. 利用Python爬虫获取招聘网站职位信息
  2. Using Python crawler to obtain job information of recruitment website
  3. Several highly rated Python libraries arrow, jsonpath, psutil and tenacity are recommended
  4. Python装饰器
  5. Python实现LDAP认证
  6. Python decorator
  7. Implementing LDAP authentication with Python
  8. Vscode configures Python development environment!
  9. In Python, how dare you say you can't log module? ️
  10. 我收藏的有关Python的电子书和资料
  11. python 中 lambda的一些tips
  12. python中字典的一些tips
  13. python 用生成器生成斐波那契数列
  14. python脚本转pyc踩了个坑。。。
  15. My collection of e-books and materials about Python
  16. Some tips of lambda in Python
  17. Some tips of dictionary in Python
  18. Using Python generator to generate Fibonacci sequence
  19. The conversion of Python script to PyC stepped on a pit...
  20. Python游戏开发,pygame模块,Python实现扫雷小游戏
  21. Python game development, pyGame module, python implementation of minesweeping games
  22. Python实用工具,email模块,Python实现邮件远程控制自己电脑
  23. Python utility, email module, python realizes mail remote control of its own computer
  24. 毫无头绪的自学Python,你可能连门槛都摸不到!【最佳学习路线】
  25. Python读取二进制文件代码方法解析
  26. Python字典的实现原理
  27. Without a clue, you may not even touch the threshold【 Best learning route]
  28. Parsing method of Python reading binary file code
  29. Implementation principle of Python dictionary
  30. You must know the function of pandas to parse JSON data - JSON_ normalize()
  31. Python实用案例,私人定制,Python自动化生成爱豆专属2021日历
  32. Python practical case, private customization, python automatic generation of Adu exclusive 2021 calendar
  33. 《Python实例》震惊了,用Python这么简单实现了聊天系统的脏话,广告检测
  34. "Python instance" was shocked and realized the dirty words and advertisement detection of the chat system in Python
  35. Convolutional neural network processing sequence for Python deep learning
  36. Python data structure and algorithm (1) -- enum type enum
  37. 超全大厂算法岗百问百答(推荐系统/机器学习/深度学习/C++/Spark/python)
  38. 【Python进阶】你真的明白NumPy中的ndarray吗?
  39. All questions and answers for algorithm posts of super large factories (recommended system / machine learning / deep learning / C + + / spark / Python)
  40. [advanced Python] do you really understand ndarray in numpy?
  41. 【Python进阶】Python进阶专栏栏主自述:不忘初心,砥砺前行
  42. [advanced Python] Python advanced column main readme: never forget the original intention and forge ahead
  43. python垃圾回收和缓存管理
  44. java调用Python程序
  45. java调用Python程序
  46. Python常用函数有哪些?Python基础入门课程
  47. Python garbage collection and cache management
  48. Java calling Python program
  49. Java calling Python program
  50. What functions are commonly used in Python? Introduction to Python Basics
  51. Python basic knowledge
  52. Anaconda5.2 安装 Python 库(MySQLdb)的方法
  53. Python实现对脑电数据情绪分析
  54. Anaconda 5.2 method of installing Python Library (mysqldb)
  55. Python implements emotion analysis of EEG data
  56. Master some advanced usage of Python in 30 seconds, which makes others envy it
  57. python爬取百度图片并对图片做一系列处理
  58. Python crawls Baidu pictures and does a series of processing on them
  59. python链接mysql数据库
  60. Python link MySQL database