#Decorators
#must know Firstclass Function and closure.
#A Decorator is just a function takes another function as arguments, adds some kind of functionality then returns another function,
#all of this without altering the source code of tne original function you passed in.
def decorator_func(original_func):
def wrapper_func():
print('wrapper function ran before {0}'.format(original_func.__name__))
return original_func()
return wrapper_func
def display_func():
print('Display Function Ran')
decorated_display=decorator_func(display_func)
#first decorator_func gets executed and assigning display_func to original_func and returns wrapper_func object and
#gets stored in decorated_display function.
decorated_display()
#when decorated_display func which is wrapper_func gets executed printing the message inside wrapper_func and
#executing original function which is display_func and printing the code inside it.
#same as above
def decorator_function(original_function):
def wrapper_function():
print('wrapper function ran before {0}'.format(original_function.__name__))
return original_function()
return wrapper_function
@decorator_function #same as, display =decorator_function(display)
def display():
print('Display Function Ran')
display()
def decorator_function(original_function):
def wrapper_function():
print('wrapper function ran before {0}'.format(original_function.__name__))
return original_function()
return wrapper_function
@decorator_function
def display_info(name,age):
print('display_info ran with arguments ({0} {1})'.format(name,age))
display_info('kushagra',23)
#will display error " wrapper_function() takes 0 positional arguments but 2 were given" bcoz wrapper_function doesnt take any argument.
def decorator_function(original_function):
def wrapper_function(*args,**kwargs):
#by adding argument *args and **kwargs.. function will take any number of positional argument and keyord arguemnts
print('wrapper function ran before {0}'.format(original_function.__name__))
return original_function(*args,**kwargs)
return wrapper_function
@decorator_function #same as, display =decorator_function(display)
def display():
print('Display Function Ran')
@decorator_function
def display_info(name,age):
print('display_info ran with arguments ({0} {1})'.format(name,age))
display()
display_info('kushagra',23)
#Using Decorator Class instead of Decorator Function
class decorator_class(object):
def __init__(self, original_function):
self.original_function= original_function
def __call__(self, *args, **kwargs):
print('class method ran before {0}'.format(self.original_function.__name__))
return self.original_function(*args,**kwargs)
@decorator_class
def display():
print('Display Function Ran')
@decorator_class
def display_info(name,age):
print('display_info ran with arguments ({0} {1})'.format(name,age))
display()
display_info('kushagra',23)
#Usecase example
def my_timer(original_func):
import time
def wrapper_func(*args, **kwargs):
t1=time.time()
result=original_func(*args,**kwargs)
t2=time.time() - t1
print('{} ran in {} sec'.format(original_func.__name__,t2))
return result
return wrapper_func
@my_timer
def display_info(name,age):
import time
time.sleep(1)
print('display_info ran with arguments ({0} {1})'.format(name,age))
display_info('kushagra',23)
@decorator
def function():
pass
is equivalent to
function = decorator(function)
#Decorators with Arguments
def prefix_decorator(prefix):
def decorator_func(original_func):
def wrapper_func(*args,**kwargs):
print(prefix, 'Executed before:', original_func.__name__)
result=original_func(*args,**kwargs)
print(prefix, 'Executed after:', original_func.__name__)
return result
return wrapper_func
return decorator_func
@prefix_decorator('LOG')
def display_info(name,age):
print('display_info ran with arguments ({0} {1})'.format(name,age))
display_info('kushagra', 30)
#for better understanding decorator
display1=prefix_decorator('LOG') #first prefic_decorator func gets executed with LOG as an argument returning decorator_func and storing as an object in display1 variable.
display2=display1(display_info) #display1 function which is decorator_func is executed with argument display_info function. original_func equals to display_info func. and returns wrapper_func.
display2('yo',24) #wrapper func takes arguments print "executed before" and pass it to original func which is display function prints display_function and prints "executed after"
#you can but you shouldn't write this way
prefix_decorator('LOG')(display_info)('yo',24)