learn python decorators code example

Example 1: decorator python

def our_decorator(func):
    def function_wrapper(x):
        print("Before calling " + func.__name__)
        func(x)
        print("After calling " + func.__name__)
    return function_wrapper

@our_decorator
def foo(x):
    print("Hi, foo has been called with " + str(x))

foo("Hi")

Example 2: python decorator

#Decorator are just function that take function as first
#parameter and return a function
def logging(f):
  def decorator_function(*args, **kwargs):
    print('executing '+f.__name__)
    return f(*args, **kwargs)
  return decorator_function
#Use it like this
@logging
def hello_world():
  print('Hello World')
#calling hello_world() prints out:
#executing hello_world
#Hello World

Example 3: python decorator

import functools

# A decorator is a Higher order function "_with_logging"
# It takes the function to be decorated as its argument
# In order to pass in some arbitrary arguments, it must be wrapped into
# another HOF (Higher order function) that will receive the inputs
def with_logging(level=logging.DEBUG, msg = None):
    def _with_logging(fn):
        # 'wraps' is a HOF that will give fn's name and docs to decorated_fn i.e. 
        #   decorated_fn.__name__ = fn.__name__
        #   help(decorated_fn) = help(fn)
        @functools.wraps(fn)
        def decorated_fn(*args, **kwargs):
            res = fn(*args, **kwargs)
            print("\n***************", f"\n{msg}", "\nExecuting with Args: ", *args, **kwargs)
            logging.log(level, res)
            return res
        return decorated_fn
    return _with_logging
  
# Used this way
@with_logging(level=logging.DEBUG, msg="Some awesome comment")
def hello_world(name):
  return f'Hello World {name}'
  
# Results after calling hello_world("John")
#
# ***************
# Some awesome comment
# Executing with Args: John
# Hello World John