What are the examples of python custom functions?-Python Tutorial-php.cn

What are the examples of python custom functions?

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What are the examples of python custom functions?

Examples of python custom functions include:

1. What is a function?

A function is an organized, reusable code segment used to implement a single or related function. Functions can improve application modularity and code reuse.

2. Function definition method:

def test(x): '函数定义方法' x+=1 return x

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Explanation:

def: Define function keywords

test: Function name

(): Definable formal parameters

'': Document description

x =1: Code block or program processing logic

return:End and return value

Why should a function have a return value? ?

Receive the execution result of the function through the return value, and subsequent logic needs to use this result to perform its corresponding operation.

(1), Example: Write log information to a file

import time # 定义函数 def test1(): '函数练习:添加日志记录' log_time = time.strftime('%Y-%m-%d %X') with open('file_a','a') as f: f.write(log_time+':log msg\n') # 调用函数 test1()

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(2), Function return value description:

return Number of return values = 0: Return one None value (none)

Return value = 1: Object (Object)

rebate Value & GT; :

#函数返回类型 def test_None(): print('返回一个空值') x=test_None() print(x) def test_object(): print('返回一个对象') return 0 y=test_object() print(y) def test_tuples(): print('返回一个元组') return 1,'hello world',['qwe','asd'],{'001':'simple'} z=test_tuples() print(z)

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(3), formal parameters: the defined parameters are called formal parameters (x, y)

Actual parameters: the actual parameters passed in are called actual parameters (1,2)

Without specifying parameters: one-to-one correspondence between actual and formal parameter positions

Example:

Note: When positional parameters are shared and keyword parameters are shared, keyword parameters cannot be written. Before positional parameters

def test_sum(x,y): '两数之和' z = x + y return z t_sum=test_sum(1,2) #实参与形参位置一一对应 print(t_sum) t_sum2=test_sum(x=1,y=2) #与形参位置无关 print(t_sum2) t_sum3=test_sum(1,y=2) # 错误方式：test_sum(x=1,2) 位置传参与关键字传参共用时，关键参数不能写在位置参数之前 print(t_sum3)

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(4), default value parameter:

# 默认值参数 def test_default(x,y=2): '默认值参数' z = x + y return z print(test_default(2)) #print(tesst_default(2,2))

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(5), parameter group (indefinite length parameter):

# 参数组,接受位置参数，将多个实参存入一个元组中 # 定义格式：*变量名(一般规范为 *args) def test_group(*args): '参数组' print(args) test_group(1,2,3,4,5,6) def test_group2(x,*args): '参数组与位置参数混用' print(x) print(args) test_group2(1,2,3,4,5,6) # 接受关键字参数组，转换成字典 def test_group3(**kwargs): '参数组键值对形式' print(kwargs['name']) test_group3(name='simple',age=25,sex='m') def test_group4(name,**kwargs): '参数、参数组键值对混用' print(name) print(kwargs) test_group4('simple',age=25,sex='m') #注：参数组必须放在位置参数、默认参数之后 def test_group5(name,age=25,**kwargs): '参数、默认参数、参数组键值对混用' print(name) print(age) print(kwargs) test_group5('simple',age=3,sex='m',game='lol') def test_group6(name,age=25,*args,**kwargs): '参数、默认参数、参数组、参数组键值对混用' print(name) print(age) print(*args) print(kwargs) test_group5('simple',age=3,sex='m',game='lol')

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