I. Definition Function

Recycled tools
to complete a particular function block, a function block of the storage container is

Second, the grammatical function

Function of four parts

Based on the use of the function: function name
Function body: completion code block
Returns: the result of feedback functions are performed
Parameters: complete information required function condition

To declare a function with the def keyword

def 函数名(参数们):
    函数体
    return '返回值'

Third, use the function

Function name: function to get the address of the
function name (): get the address of a function, and executes the code stored in the block function (function body) *****
function name (parameter): pass parameters and perform functions

Function name (): When finished, will be the return value of the function, the return value just like ordinary variables, can print directly, use, operation

def fn(num):
    print("传入的num值：%s" % num)
    return '收到了'

res = fn(10) #  控制台会打印：传入的num值：10     res的值为：'收到了'

Note: you must first define the function call

Fourth, the classification function

1. The parameter list is divided

No-argument function: no external resources

def start():
    print('系统启动')
start()

There are function parameters: the need for a foreign key resources

def login(usr, pwd):
    if usr == 'owen' and pwd == '123':
        print('登录通过')
	else:
        print('登录失败')
        
 login('owen', '123')

The return value is divided

return function is used to end

Empty Returns: None

def demo(x, y):
    print( x + y )
    
def demo(x, y):
    print( x + y )
return  # 用来强行结束函数的（像break结束循环一样）

Single value is returned

  def demo(x, y):
    return x + y

Multi-value return

def demo(x, y):
return x + y, x - y, x * y, x / y # 本质就是返回装有多个值的元组

Fifth, the nested function calls

example

# 求两个数最大值
def max_2(n1, n2):
    if n1 > n2:
        return n1
    return n2

求三个数最大值
def max_3(n1, n2, n3):
    m2 = max_2(n1, n2)
    return max_2(m2, n3)

求四个数最大值
def max_4(n1, n2, n3, n4):
    m2 = max_2(n1, n2)
    return max_3(m2, n3, n4)

Cycle call: calling another function within a function

Cornerstone Qinnengbuzhuo labyrinth tour - the ninth day (Python function Preliminary)