Decorator

decorators.py

import functools
import os


## Example 1: 
'''
Decorator functions are great ways to template-ize a piece of functional
code that should be run before / after any other function. For example,
checking permissions or connections to a DB could be put into a decorator
and reused before all other functions.
'''
def my_decorator(func):  # Consumes a function as the argument
 
    @functools.wraps(func)  # Always include this with the argument above
    def additional_function():
        print('This is some pre-function code!')  # Executes first
        func()  # Always call your function
        print('This is some post-function code!')
    return additional_function


@my_decorator  # syntactic sugar to feed function into decorator function above
def my_original_function():
    print('This is my original function doing things!')  
    
    
my_original_function()


## Example 2: Args for a Decorator
os.environ['USER_KEY'] = 1234

def my_decorator_plus_args(num):
    def my_other_decorator(func):
        user_key = os.environ['USER_KEY']

        @functools.wraps(func)
        def additional_function():
            if num == user_key:
                func()
            else:
                print('USER KEY INCORRECT!!!')
        return additional_function
    return my_decorator


@my_decorator_plus_args(1111)
def my_data_processing_function():
    print('Robert); DROP TABLE Students;')
    
my_data_processing_function()

# Example 3: Passing Args from Function through Decorator

os.environ['USER_KEY'] = 1234

def my_decorator_plus_args(num):
    def my_other_decorator(func):
        user_key = os.environ['USER_KEY']

        @functools.wraps(func)
        def decorating_function(*args, **kwargs):  # accepts all positional and keywords coming in (i.e. def fun(4, 5, eye='brown'))
            if num == user_key:
                print('decorator doing its duty')
                func(*args, **kwargs)
                print('function ran')
            else:
                print('USER KEY INCORRECT!!!')
        return additional_function
    return my_decorator
        
@my_decorator_plus_args(1234)
def basic_function_with_args(height, weight):
    print('my height: {}\nmy weight: {}'.format(height, weight))