Python---functions

function Features: Reduce duplication of code, make programs extensible, and make programs easier to maintain

1. Defining Functions

#定义函数def func1 (): "" "Test" "Print (" This is Test ") return 0# defines the procedure #通俗的说过程就是没有返回的函数, but Python returns a none Def func2 (): "" "Test1" "" Print ("This is Test") #调用函数x = func1 () y = Func2 () #打印函数返回值print (x, y) #0 None

2. function return value

#函数返回值作用: Determines the execution of the function.                                    def test1 (): Print ("This was test") #返回nonedef test2 (): Print ("This is Test") return 0 #返回0def test3 (): Print ("This is Test") return 1, "Hello", ["a", "B"],{"a": "B"} #返回 One tuple x = test1 () y = test2 () z = test3 () print (x) print (y) print (z)

3. Function parameters

#1. Positional parameters and keyword parameters def test1 (x, Y, z):     print (×)     print (y)      print (z) test1 (a)          #位置参数, in order about Test1 (y=2,z=3 , x=1)    #关键字参数, location independent test1 (1,z=3,y=2)      #既有位置参数, and the keyword parameter, the positional parameter cannot be preceded by the keyword parameter. def  test2 (x,y=2):     print (x)     print (y) test2 (1)               #如果不指定y, the default value is used, and the new value is specified with the new value test2 (1,3) test2 (1,y=3) #3. Parameter Group def  test3 (*args):        #将传入值转化成一个元组     print (args) Test3 (1,2,3,4,5) test3 (*[1,2,3,4,5]) #输出 #  (1, 2, 3, 4, 5) #  (1, 2, 3,  4, 5) Def test4 (X,*args):     print (x)     print (args) Test4 (1,2,3,4,5) #输出 # 1#  (2, 3, 4, 5) def test5 (**kwargs):          #将 "OffThe key-word parameter "translates into a dictionary     print (Kwargs) test5 (y=1,x=2,z=3) #输出 # {' y ': 1,  ' x ':  2,   ' Z ':  3}def test6 (Name,age=18,**kwargs):     print (name)      print (age)     print (Kwargs) test6 ("Feng", y=1,x=2) #输出 # feng# 18# {' y ':  1,  ' x ':  2}test6 ("Feng", 23,y=1,x=2) #输出 # feng# 23# {' x ': 2,  ' y ':  1 }

4. Local variables and global variables

name1 = "Fengxiaoli" #全局变量, in effect for all functions, if the global variable defines a string or a number, then only local after local modification, Def test (): #对全局还是没生效, if the global variable definition is the dictionary, list, collection, class, then after the local modification to the global also take effect #global name #在函数中声明全局变量, with caution name1 = "CX" #局部变量, only in the function in effect prin T (name1) test () print (name1) # output: # cx# fengxiaoliname2 = ["CX", "Fengxiaoli"]def test2 (): name2[0] = "CX" Print (name2) t Est2 () print (name2) # output: # [' CX ', ' Fengxiaoli ']# [' cx ', ' Fengxiaoli ']

5. Recursive function

#递归特性: There must be a definite end condition. Each time a deeper recursion is reached, the problem size should be reduced compared to the previous recursion. Recursive efficiency not high Def calc (n): print (n) if int (N/2) >0:return (Calc (int (N/2))) Calc (10)

6. High-order function

#变量可以指向函数, the function's parameters can receive the variable, then one function can receive another function as a parameter, which is called the high order function Def test (a,b,f): res = f (a) +f (b) Print (RES) test ( -5,3,abs) #这里的abs是一个求绝对值的函数

7. Anonymous function

Calc = Lambda x:x*3print (Calc (3))

Python---functions