Python-- basis functions

What is the function

　　Functions like Lego different shapes, can play our own imagination to be assembled using.

　　Defined functions need to achieve with the def keyword.

Let's look at an example:

DEF Demo ():
     Print ( " Hello everyone, I am a function " )
     Print ( " I said he was excited " ) 
Demo ()

View Code

 Note: At the time of writing after the function must be to pay attention to a small parenthesis, defined functions use def, finally, make the call.

 Function parameters

　　Examples of parameters that make it possible to personalize the function, with this function parameter becomes a variable.

Look instance:

def Demo(num,num2):
    result = num + num2
    print(result)
Demo(1,2)

View Code

Note: If you want to use multiple parameters (at English) "," can be achieved.

Function's return value

　　The return value is to use the function to return some of the data or the result for us.

Example:

def Dome(num,num2):
    return num+num2
print(Dome(1,2))

View Code

Note: All functions have a default value returns under most cases, result in a return to return to function without using print Print

Local and global variables

　　Local variables

　　　　Defined in the function parameters are called local variables inside 

Example:

DEF Demo (One, TOW): 
    the Result = One * TOW 
    return the Result 
NUM = float (the INPUT ( "Please enter a price:")) 
num2 = float (the INPUT ( "How many fold playing:")) 
A = Demo (NUM, num2 ) 
Print ( "discounted price:% S"% a) 
Print ( "Print where the value of the local variable result:% s"% result)

 When performing code error line 8, because the result is a local variable, its scope is only effect this demo function inside,

 A demo outside this range can not output the result, result can only take effect in the local inside.

　　Global Variables　　

 　　　　In the beginning of the program defined variable called global variables

 Example:

DEF Demo (One, TOW): 
    the Result = One * TOW 
    Print ( "NUM value print global variables:% S"% NUM) 
    return the Result 
NUM = float (the INPUT ( "Please enter a price:")) 
num2 = float (the INPUT ( "how to play off:")) 
a = Demo (NUM, num2) 
Print ( "discounted price:% s"% a)

Note: python where you can go to access the global variables in the function but not to modify global variables,

　　　Try to modify the global variable in a function, python will automatically create a new local variable to replace.

Example:

1  DEF Demo (One, TOW):
 2      Result = One * TOW
 . 3      num = 50
 . 4      Print ( " after a modified num value:% S " % num)
 . 5      return Result
 . 6 num = a float (INPUT ( " Please enter a price : " ))
 . 7 num2 = a float (INPUT ( " hit number off: " ))
 . 8 a = Demo (num, num2)
 . 9  Print ( " value of the num after 2 modifications:% S " % num)
 10  Print ( " price after discount:% s" % a)