27rohitb.github.io

REMEMBER: putting brackets will EXECUTE the function.

Decorators

It is a function that takes in some_func as an argument, adds some functionality to it and returns it, all this, WITHOUT making any change to the original source of the some_func.

Simplest form:

Definition:

def decorator_func(some_func):
	def wrapper_function():
        #TODO something with some_func
        return some_func(*args, **kwargs )
    return wrapper_func

Usage:
decorated_some_func = decorator_func(some_func)

Complicated form:

This will automatically decorate some_func

@decorator_func
def  some_func(some_params):
	#TODO

Note:

• *args -> lets us pass any number of arguments.
• **kwargas -> lets us pass any number of keyword arguments.

Classes as decorators

class dec_class(object):
	
	def __init__(self, some_func):
		self.some_func = some_func
		//to initalize function
	
	def __call__(self, *args, **kwargs):
		//code of wrapper_function goes here
        return self.some_func(*args , **kwargs)

Multiple Decorators

Multiple decorators can be used , by stacking them up on a single function,but using multiple decorators at once can have unintended consequence, hence use:

from functools import wraps

@warps(some_func)
before every wrapper_func for all decorators

DECORATORS WITH ARGS

Arguments can be passed to decorator, but this requires another level of sopohstication.

def prefix_dec(some_var):
	def actual_dec(some_func):
		def wrapper_func(*args, **kwargs):
			#TODO
		    return some_func()
	    return wrapper_func
    return actual_dec

Usage example:

@actual_dec(some_var)
def some_func:
	#TODO