table of Contents

1. Definition Function

def 函数名（等同于变量名）():
    '''对函数的描述信息'''
    code

Characteristics defined functions: a function definition process, only detect syntax, the code is not performed. When you call the function, it executes the code

2. Define the functions of three ways

No-argument function

def hanshu():
    x = 10
    y = 10
    print(x>y) #函数中有代码块

There are function parameters

def hanshu(x,y):
    print(x>y) #函数中有代码块

Call a function is to use the function

def hanshu():
    x = 10
    y = 10
    print(x>y) #函数中有代码块
hanshu()   #函数名加()   调用函数
print(hanshu)   #直接打印函数名 ：打印结果为函数的内存地址

Once you have defined the function, call the function return value there. The return value of the function defaults to None

We use return to return the function's return value. The return value can be any data type

def hanshu(x):
    x = x+10
    return x
y = hanshu(1)
print(y+10) # 打印结果为 21

return characteristics:

return is a return value, if there is no return value, default return None
return terminates the function, the following code will not run return, assuming there are multiple return, ran to meet the conditions of return would not run when other return
return can return multiple values, return values received in the form of a tuple

Defining a function is generated, the function name in parentheses.

Receiving from left to right argument

When the value is not passed to the default parameter values, the default value, if the value passed to it, it is passed in use
The default parameter behind only on the position of the parameter

In parentheses when calling a function function name

From left to right to pass parameter values, parameter number, the number of arguments must

下面的可变长形参中   *   后面是一个类似变量名的东西，可以随便写

def hanshu(*lis): #  *lis  把所有传过来的所有实参按元组的形式存储， 如果 *lis 的前面存在其他形参，那么 *lis 接收的就是剩下的实参
    a,b,c,d,*_ = lis  # 以解压缩的方法取出想要的值
    print(a,b,c,d)

def hanshu(*lis):
    print(max(lis))
lt = [1,2,3,4,5,6]
res = hanshu(*lt)  #   * 相当于解压缩，也就是把lt内的元素一个一个取出来传给形参