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Commit b8ef046

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Decorators
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‎08.Decorators/decorators-1.py

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#decorators-1.py
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# Decorators, as simple as it gets :)
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# Decorators are functions that compliment other functions,
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# or in other words, modify a function or method.
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# In the example below, we have a function named `decorated`.
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# This function just prints "This happened".
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# We have a decorator created named `inner_decorator()`.
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# This decorator function has an function within, which
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# does some operations (print stuff for simplicity) and then
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# returns the return-value of the internal function.
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# How does it work?
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# a) The function `decorated()` gets called.
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# b) Since the decorator `@my_decorator` is defined above
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# `decorated()`, `my_decorator()` gets called.
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# c) my_decorator() takes a function name as args, and hence `decorated()`
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# gets passed as the arg.
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# d) `my_decorator()` does it's job, and when it reaches `myfunction()`
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# calls the actual function, ie.. decorated()
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# e) Once the function `decorated()` is done, it gets back to `my_decorator()`.
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# f) Hence, using a decorator can drastically change the behavior of the
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# function you're actually executing.
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def my_decorator(my_function): # <-- (4)
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def inner_decorator(): # <-- (5)
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print("This happened before!") # <-- (6)
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my_function() # <-- (7)
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print("This happens after ") # <-- (10)
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print("This happened at the end!") # <-- (11)
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return inner_decorator
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# return None
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@my_decorator # <-- (3)
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def decorated(): # <-- (2) <-- (8)
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print("This happened!") # <-- (9)
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if __name__ == "__main__":
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decorated() # <-- (1)
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'''
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O/P-
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This happened before!
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This happened!
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This happens after
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This happened at the end!
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'''

‎08.Decorators/decorators-2.py

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# decorators-2.py
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# An updated version of decorators-1.py
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# This code snippet takes the previous example, and add a bit more information
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# to the output.
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import datetime
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def my_decorator(inner):
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def inner_decorator():
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print(datetime.datetime.utcnow())
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inner()
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print(datetime.datetime.utcnow())
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return inner_decorator
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@my_decorator
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def decorated():
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print("This happened!")
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if __name__ == "__main__":
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decorated()
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'''
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O/P: (NOTE: The time will change of course :P)
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2022年07月16日 12:24:18.704572
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This happened!
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2022年07月16日 12:24:18.704572
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'''

‎08.Decorators/decorators-3.py

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# This is an updated version of decorators-2.py.
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# Here, the `decorated()` function takes an argument
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# and prints it back on terminal.
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# When the decorator `@my_decorator` is called, it
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# takes the function `decorated()` as its argument, and
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# the argument of `decorated()` as the argument of `inner_decorator()`.
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# Hence the arg `number` is passed to `num_copy`.
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import datetime
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def my_decorator(inner):
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def inner_decorator(num_copy):
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print(datetime.datetime.utcnow())
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inner(int(num_copy) + 1)
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print(datetime.datetime.utcnow())
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return inner_decorator
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@my_decorator
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def decorated(number):
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print("This happened : " + str(number))
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if __name__ == "__main__":
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decorated(5)
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'''
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O/P-
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2022年07月16日 12:26:14.060603
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This happened : 6
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2022年07月16日 12:26:14.060603
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'''

‎08.Decorators/decorators-4.py

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#decorators-4.py
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# This example builds on the previous decorator examples.
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# The previous example, decorators-3.py showed how to
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# deal with one argument passed to the function.
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# This example shows how we can deal with multiple args.
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# Reminder : `args` is a list of arguments passed, while
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# kwargs is a dictionary passed as arguments.
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def decorator(inner):
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def inner_decorator(*args, **kwargs):
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print(args, kwargs)
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return inner_decorator
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@decorator
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def decorated(string_args):
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print("This happened : " + string_args)
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if __name__ == "__main__":
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decorated("Hello, how are you?")
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# This prints :
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# # python 22-decorators-4.py
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# ('Hello, how are you?',)

‎08.Decorators/decorators-5.py

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#decorators-5.py
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from __future__ import print_function
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# 2. Decorator function
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def handle_exceptions(func_name):
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def inner(*args, **kwargs):
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try:
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return func_name(*args, **kwargs)
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except Exception:
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print("An exception was thrown : ", Exception)
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return inner
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# 1. Main function
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@handle_exceptions
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def divide(x, y):
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return x / y
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print(divide(8, 0))
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'''
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O/P-
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An exception was thrown : <class 'Exception'>
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None
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'''

‎08.Decorators/decorators-6.py

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def decorator(inner):
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def inner_decorator(*args, **kwargs):
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print("This function takes " + str(len(args)) + " arguments")
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inner(*args)
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return inner_decorator
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@decorator
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def decorated(string_args):
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print("This happened: " + str(string_args))
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@decorator
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def alsoDecorated(num1, num2):
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print("Sum of " + str(num1) + "and" + str(num2) + ": " + str(num1 + num2))
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if __name__ == "__main__":
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decorated("Hello")
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alsoDecorated(1, 2)
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'''
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O/P-
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This function takes 1 arguments
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This happened: Hello
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This function takes 2 arguments
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Sum of 1and2: 3
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'''

‎08.Decorators/decorators-7.py

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#decorators-7.py
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# We have two functions, one which adds two numbers,
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# and another which subtracts two numbers.
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# We apply the decorator @double which takes in the
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# functions that is called with the decorator, and doubles
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# the output of the respective function.
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def double(my_func):
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def inner_func(a, b):
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return 2 * my_func(a, b)
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return inner_func
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@double
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def adder(a, b):
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return a + b
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@double
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def subtractor(a, b):
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return a - b
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print(adder(5, 6)) #22
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print(subtractor(8, 2)) #12

‎08.Decorators/decorators-class.py

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#class-decorators.py
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# Till the previous examples, we saw function decorators.
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# But decorators can be applied to Classes as well.
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# This example deals with class decorators.
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# NOTE: If you are creating a decorator for a class, you'll it
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# to return a Class.
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# NOTE: Similarly, if you are creating a decorator for a function,
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# you'll need it to return a function.
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def honirific(cls):
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class HonirificCls(cls):
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def full_name(self):
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return "Ms." + super(HonirificCls, self).full_name()
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return HonirificCls
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@honirific
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class Name(object):
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def __init__(self, first_name, last_name):
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self.first_name = first_name
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self.last_name = last_name
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def full_name(self):
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return " ".join([self.first_name, self.last_name])
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result = Name("Shikha", "Pandey").full_name()
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print("Full name: {0}".format(result))
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#Full name: Ms.Shikha Pandey
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# This needs further check. Erroring out.

‎README.md

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05. [Inheritance](https://github.com/Shikha-code36/Object-Oriented-Programming-OOPs-Python#05-inheritance)
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06. [Encapsulation](https://github.com/Shikha-code36/Object-Oriented-Programming-OOPs-Python#06-encapsulation)
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07. [Polymorphism](https://github.com/Shikha-code36/Object-Oriented-Programming-OOPs-Python#07-polymorphism)
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08. [Decorators](https://github.com/Shikha-code36/Object-Oriented-Programming-OOPs-Python#08-decorators)
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------------
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## What do you understand by OOPs?
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[Detailed Explanation](07.Polymorphism)
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------------
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------------
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#### 08. Decorators
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A decorator takes in a function, adds some functionality and returns it.
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Decorators are used to add functionality to an existing code.
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This is also called metaprogramming because a part of the program tries to modify another part of the program at compile time.
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[Detailed Explanation](08.Decorators)
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