python static methods and class methods, decorators

First, static methods and class methods

1. static call: @staticmethod

class A(object):
    @staticmethod
    def a():
        print('a')
A.a()

　　If you need presence of non-class members of the class, you can use the static method call

2. Example

It is determined whether an input is the four sides of the square, if it is: calculating the area, with @staticmethod

class zfx(object):
    def __init__(self,a,b,c,d):
        self.a=a
        self.b=b
        self.c=c
        self.d=d
    @staticmethod
    def is_valid(a,b,c,d):
        for i in [b,c,d]:
            if i !=a:
                return False
        else:
            return True
    
    def area(self):
        if res == True:
            area_ = self.a *self.b
            return area_

fx = zfx(5,5,5,5)
res = fx.is_valid(5,5,5,5)
fx.area()
if res == True:
    print(fx.area())

3. Class Methods

(1) Default:

def A(bl = 'hello'):
    print(bl)
A()

　　The output is: hello

（2）cocaltime

# Localtime call the library: 
from Import Time Time, localtime, SLEEP 
Print (Time ())

　　Time stamp, from January 1, 1970 00.00.00 number of seconds to start now experienced

（3）@classmethod

@classmethod: Get Class itself (cls) attributes, and can be changed.
a classmethod modifiers need not instantiate the corresponding function, no self parameters, but the first parameter is a required parameter itself cls class can be invoked attribute class, the class methods, and other objects instantiated

Relationship (inherited) between the Class 4 Class

(1) The first step is to write the name of the class inherited class

(2) the class name suggested (classname) __ init __ (self): a .__ init __ (self)

(3) Example: Create a parent class to create a subclass, the parent and two numbers calculated sum_, print this subclass sum_

class fu(object):
    def __init__(self):
        self.a = 10
        self.b = 20
    def sum_(self):
        sum=self.a + self.b
        return sum
class zi(fu):
    def __init__(self):
        fu.__init__(self)
    def PRINT(self):
        res = self.sum_()
        print(res)
b= zi()
b.PRINT()

　　Output: 30

The list and the list production unit formula

# List formula 
A = [X for X in Range (100)] 
    Print (A) 
# list generator 
A = (X for X in Range (100)) 
    Print (A)

　　List Builder List Builder type with advantages and disadvantages:

(1) formula:

Advantages: fast calculation, as have all-time loaded into memory, the data volume is not too large for the case 10000-2000-
disadvantages: memory for

(2) Generator:

Advantages: save memory
disadvantages: slow calculation as to generate

Second, the decorator

1. decorator usage

Go walk decorator function

Example 2. decorator: create three functions, two parameters, the decorator and the processing of these two parameters, each of the print function of these two parameters

Joker DEF (FUNC): 

DEF Warp (N1, N2, N3): 

NUM = N1 + N2 

return FUNC (0, NUM, N3) 

return Warp 



* decorator summing the first two digits, the first function itself multiplied by the three parameters and * 

@Joker 

DEF SUM (num1, num2, num3): 

Print (num1, num2, num3) 

Print (num2 * num3) 



SUM (10,2,3)

python static methods and class methods, decorators

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