Popular speaking ： So called functions , It refers to a piece of code that implements specific functions “ take ” A name , You can go through This name is used to execute （ call ） This function
From function definer （ People who implement functions ） From the perspective of , At least it needs to think clearly 3 spot ：
Functions need several key data that need to change dynamically , These data should be defined as parameters of the function
The internal implementation of the function
The function needs to send out several important data （ It's the data that the caller wants ）, These data should be Defined as the return value
Function definition and call
You have to define a function before you can use it The syntax format for defining functions is as follows ：
Def Function name （ Parameter list ）
Function statement
Return Return value
Call function ： Function name （ Shape parameter ）
Python Declaration functions must use def keyword , A detailed description of the function syntax format is as follows ：
Function name ： From a grammatical point of view , A function name needs only a legal identifier , From a program's readability point of view , The function name should be composed of one or more meaningful words , The letters of each word are all lowercase , Words and words Use underline to separate
Parameter list ： Used to define the parameters that the function can receive , The parameter list consists of multiple parameter names , Name of multiple formal parameters Use English commas （, ） separate , Once the parameter list is specified when defining a function , When you call this function, you must pass The corresponding parameter value , in other words , Who calls the function and who is responsible for the assignment of parameters
Function statement part ： When you receive a formal parameter , How to calculate formal parameter data , That is, the code part
Return part ： When your code is calculated , The data that needs to be returned to the caller , If... Is not specified in the definition return Parameters , The function will not return the result after the operation . In the function , return After the code , It won't run again
Return Return multiple values
If the program needs to have multiple return values , You can wrap multiple values into a list and return , Multiple values can also be returned directly If python Function returns multiple values directly , python Will automatically encapsulate multiple return values into meta groups
Format ： return value 1 , value 2 , value 3 （ The value can be a number , character string , Variable , Array , Dictionary, etc ）
If multiple values are returned , It can also be received separately with multiple variables
example ： x The function throws two values , Can be received ： a , b=x （ ） The first value will be given a , The second value will give b
Write a function , Implement the passed in array , If the passed in parameter is an integer or decimal , Just add up the values , Sum and average
c=[1,2,3,4,5]
def test(test):
sum=0
count=0
for i in test:
if isinstance(i,int) or isinstance(i,float):
sum+=i
count+=1
return sum,sum/count
a,b=test(c)
print(a,b)
Find the even number , Encapsulated in a function , Implement the passed in array , Automatically calculate even numbers
def w(a):
x=[]
for i in a:
if isinstance(i,int)or isinstance(i,float):
x.append(i)
n=[]
for q in x:
if q%2==0:
n.append(q)
print(n)
return n
a=[1,2,4,5,7,1234,123,45,24,46,'qwer',66,0.66,62,0.66]
w(a)
When defining a variable in a program , This variable has a scope , The scope of a variable is called its scope . According to the position of the defined variable , There are two kinds of variables ： local variable ： Variables defined in functions , Including the parameters , Are called local variables . Local variables are only valid within functions
Global variables ： Outside the function , Globally defined variables , Called global variables , Global variables are valid for the entire code segment .
