Logging Decorator in Python

Logging is very important in software development. Tracking events, debugging & application analysis is performed using Logging.

Python comes with standard module logging which implements logging system for applications and libraries.

In this Python program, we design logger decorator without using logging module. This decorator then can be used to decorate function which logs some message. For now message is printed in standard output but you can modify to store it into file or database.

Python Source Code: Logger Decorator

# Logger decorator

def logger(fn):
    from datetime import datetime, timezone
    
    def inner(*args, **kwargs):
        called_at = datetime.now(timezone.utc)
        to_execute = fn(*args, **kwargs)
        print('{0} executed. Logged at {1}'.format(fn.__name__, called_at))
        return to_execute
    
    return inner

@logger
def function_1():
    pass

@logger
def function_2():
    pass

@logger
def function_3():
    pass

@logger
def function_4():
    pass

function_1()
function_4()
function_2()
function_3()
function_1()
function_4()

Output

function_1 executed. Logged at 2020-05-26 03:23:08.714904+00:00
function_4 executed. Logged at 2020-05-26 03:23:08.714904+00:00
function_2 executed. Logged at 2020-05-26 03:23:08.715902+00:00
function_3 executed. Logged at 2020-05-26 03:23:08.715902+00:00
function_1 executed. Logged at 2020-05-26 03:23:08.715902+00:00
function_4 executed. Logged at 2020-05-26 03:23:08.715902+00:00