Jane said function of Python

table of Contents

Python function

Like usually play with blocks, a function that is a building block to block, you can be combined in any shape you want.

Python function

Simple function call

#!/usr/bin/python
# -*- coding: UTF-8 -*-
 
def printHello():
    print("hello world!")
    print("张盛东你来了")
    
printHello()
printHello()

I can see the above-mentioned two calls to printHello()the function, save as fun01.py, implementation of the results is as follows:

G:\Py>python fun01.py
hello world!
张盛东你来了
hello world!
张盛东你来了

Function parameter passing

Here printHello(num)the contents in the square brackets, used to pass parameters (argument)

#!/usr/bin/python
# -*- coding: UTF-8 -*-
 
def printHello(num):
    print("hello world!")
    print("张盛东你来了")
    print("带了",num,"个苹果")
    
printHello(3)

A plurality of parameters can be passed, for example, three transmission parameters. as follows:

#!/usr/bin/python
# -*- coding: UTF-8 -*-
 
def printHello(num,name):
    print("hello world!")
    print("张盛东你来了")
    print("带了",num,"个苹果")
    print("叫了",name,"这位好朋友一起来吃")
    
printHello(3,'胡轲')

return value

Definition of a function, there is generally input process, an output. Think of it as a black box, what could not see. Then enter several values, returns a result.

Calculation circular area

#!/usr/bin/python
# -*- coding: UTF-8 -*-
import math
 
def area_circle(r):
    print("你传入的半径是",r)
    S =  math.pi*r**2
    return  S
r1 = 5
S1 = area_circle(r1)
print("半径为",r1,"的圆面积是",S1)

The results obtained were as follows:

G:\Py>python fun04.py
你传入的半径是 5
半径为 5 的圆面积是 78.53981633974483

Variable Scope

Local variables

What is a local variable, the variable is only used within a function, if you call out, then directly be wrong. Take area_circle()function sub Examples. as follows:

#!/usr/bin/python
# -*- coding: UTF-8 -*-
import math
 
def area_circle(r):
    print("你传入的半径是",r)
    S =  math.pi*r**2
    return  S
r1 = 5
S1 = area_circle(r1)
print("半径为",r1,"的圆面积是",S1)
####调用局部的变量r
print(r)

Save As fun05.py, perform the following effects:

G:\Py>python fun05.py
你传入的半径是 5
半径为 5 的圆面积是 78.53981633974483
Traceback (most recent call last):
  File "fun05.py", line 13, in <module>
    print(r)
NameError: name 'r' is not defined    ----->r是局部变量，不能在全局使用。

Global Variables

It may be used in full. Continue to modify area_circle()functions.

#!/usr/bin/python
# -*- coding: UTF-8 -*-
import math

###### 这里r1是全局变量。

def area_circle(r):
    print(r1,"函数内的全局变量")
    print("你传入的半径是",r)
    S =  math.pi*r**2
    return  S

r1 = 5
S1 = area_circle(r1)
print(r1,"函数外的全局变量")
print("半径为",r1,"的圆面积是",S1)

Very magical time, within the functions can also be read r1variables. Results are as follows:

G:\Py>python fun06.py
5 函数内的全局变量
你传入的半径是 5
5 函数外的全局变量
半径为 5 的圆面积是 78.53981633974483

Now let's change this, what effect the global variable functions will appear.

#!/usr/bin/python
# -*- coding: UTF-8 -*-
import math

###### 这里r1是全局变量。

def area_circle(r):
    r1 =10
    print("函数内的全局变量", r1)
    print("你传入的半径是",r)
    S =  math.pi*r**2
    return  S
r1 = 5
S1 = area_circle(r1)
print(r1,"函数外的全局变量")
print("半径为",r1,"的圆面积是",S1)

Save As fun07.py, to see results

G:\Py>python fun07.py
函数内的全局变量 10                 ---->函数内，修改的不能带出
你传入的半径是 5
5 函数外的全局变量                  ---->函数外，r1还是5.
半径为 5 的圆面积是 78.53981633974483