Decorator strange behavior [duplicate]

This is meant to calculate execution time and log / print it:

def timer(logger=None): def decorator(func): def wrapper(*args, **kwargs): start_time = perf_counter() result = func(*args, **kwargs) total_time = perf_counter() - start_time message = f'{func.__name__} Time: ' f'{total_time} seconds' if logger is not None: logger.info(message) else: print(message) return result return wrapper return decorator @timer def decorated(): print("Running ...") if __name__ == '__main__': decorated() 

I'm expecting this to print time, instead it complains about a missing argument:

TypeError: decorator() missing 1 required positional argument: 'func' 

However, when I do:

@timer(None) def decorated(): print("Running ...") 

or:

@timer(logger=None) def decorated(): print("Running ...") 

It works! what is this nonsense?

Running ... decorated Time: 2.3044999999999316e-05 seconds 

Notes:

• To those marking my question as a duplicate, can you explain why other decorators work just fine?
• In the example below, lru_cache accepts maxsize and typed parameters and works without explicit calls as well.

Example:

from functools import lru_cache @lru_cache def decorated(): print("Running ...") 

Out:

Running ...