PYTHON

class decorator python

# class decorators act in the same way as a function decorator
# but a class can maintain and update a state

class CountCalls:
    def __init__(self, func):       #class decorator __init__ takes func
        self.func = func
        self.num_calls = 0          #keep tract of how many times func got executed
    
    def __call__(self, *args, **kwargs):
        self.num_calls += 1
        print(f'This is executed {self.num_calls} times')
        return self.func(*args, **kwargs)
    
@CountCalls
def say_hello():
    print('Hello')
    
say_hello()
# This is executed 1 times
# Hello
say_hello()
# This is executed 2 times
# Hello

class decorator python

# I dont know whether the term "class decorator" is referring to
# using decorators on a class or using a class as a decorator
# so heres both!

## Using a class as a decorator ##
class TestDecorator:

    # This is called when used, func is the function or class provided:
    def __init__(self, func): 
        def wrapper(message):
            print("Wrapper Calling: ", func(message))

        return wrapper

@TestDecorator
def abc(message):
    return message.upper()


## Using a decorator on a class ##
def TestDecorator(provided_class):
    print("Given class: ", provided_class)

    return provided_class

@TestDecorator
class abc: ... 

python decorator class method

# Here is an example from https://wiki.python.org/moin/PythonDecorators#Examples

@classmethod
def foo (arg1, arg2):
   ....
   
# https://wiki.python.org/moin/PythonDecoratorLibrary has more examples 

python decorator class

# Python program showing
# use of __call__() method
 
class MyDecorator:
    def __init__(self, function):
        self.function = function
     
    def __call__(self):
 
        # We can add some code
        # before function call
 
        self.function()
 
        # We can also add some code
        # after function call.
 
 
# adding class decorator to the function
@MyDecorator
def function():
    print("GeeksforGeeks")
 
function()

use decorator in class python

class Test(object):
    def _decorator(foo):
        def magic( self ) :
            print "start magic"
            foo( self )
            print "end magic"
        return magic

    @_decorator
    def bar( self ) :
        print "normal call"

test = Test()

test.bar()