Python decorators support aspect-oriented programming. It is used to add or modify the code in functions or classes. Using decorators will provide security, tracing, looking etc Let see an example:
@fundecorator def myfunc(): print "This is my function"
The above example has a function myfunc() with a decorator @fundecorator. The symbol @ tell that the type of the name is a decorator. Some points regarding decorators: -- Decorators can be function or class -- The class that is used as a decorator must implement __call__ -- In a class, decorator arguments are optional whereas a function decorator must have arguments. Decorators are of two types: 1. Class decorators: - In this, we use class as a decorator to decorate functions/classes. For example:
>>> class mydecorator(object): ... def __init__(self, f): ... self.f = f ... def __call__(self): ... print "Start of", self.f.__name__ ... self.f() ... print "End of", self.f.__name__ ... >>> @mydecorator ... def func1(): ... print "This is function 1" ... >>> @mydecorator ... def func2(): ... print "This is function 2" ...
The output is:
>>> func1() Start of func1 This is function 1 End of func1 >>> func2() Start of func2 This is function 2 End of func2
Class decorators without arguments: The above example is considered under this category. There are no decorator arguments in __init__. So the control is passed to the constructor f() which will take the function to be decorated as input. __call__ will be invoked only after the decorated function is called. Class decorators with arguments: These are the class decorators which take input arguments. For example:
#decorators.py class mydecorator(object): def __init__(self, arg1, arg2, arg3): self.arg1 = arg1 self.arg2 = arg2 self.arg3 = arg3 def __call__(self, f): def sum_of_args(*args): print("Decorator arguments:", self.arg1, self.arg2, self.arg3) f(*args) print("Sum of decorator arguments: ", (self.arg1+self.arg2+self.arg3)) return sum_of_args @mydecorator(5, 10, 15) def sayHello(a1, a2, a3, a4): print('sayhello() arguments:', a1, a2, a3, a4) print("Calling sayHello()") sayHello("say", "hi", "hello", "world")
The output for the above program will be:
~$ python decorators.py Calling sayHello() ('Decorator arguments:', 5, 10, 15) ('sayhello() arguments:', 'say', 'hi', 'hello', 'world') ('Sum of decorator arguments: ', 30)
2. Function decorators:- In this we use function as decorator to decorate functions/classes. For example:
>>> def mydecorator(f): ... def myfun(): ... print "Start of", f.__name__ ... f() ... print "End of", f.__name__ ... myfun.__name__ = f.__name__ ... return myfun ... >>> @mydecorator ... def func1(): ... print "This is function 1" ... >>> @mydecorator ... def func2(): ... print "This is function 2" ...
The output will be same as the output for Type 1.
Micropyramid is a software development and cloud consulting partner for enterprise businesses across the world. We work on python, Django, Salesforce, Angular, Reactjs, React Native, MySQL, PostgreSQL, Docker, Linux, Ansible, git, amazon web services. We are Amazon and salesforce consulting partner with 5 years of cloud architect experience. We develop e-commerce, retail, banking, machine learning, CMS, CRM web and mobile applications.
Django-CRM :Customer relationship management based on Django
Django-blog-it : django blog with complete customization and ready to use with one click installer Edit
Django-webpacker : A django compressor tool
Django-MFA : Multi Factor Authentication
Docker-box : Web Interface to manage full blown docker containers and imagesMore...