What does the functionality of a decorator in programming provide?

A decorator in programming is a construct that allows modifying or extending the behavior of a function or method without changing their source code. In Python, decorators are implemented as functions that take another function and return a new function with added functionality.

Example of using a decorator for logging function calls:

def log_decorator(func):
    def wrapper(*args, **kwargs):
        print(f"Calling function {func.__name__} with arguments {args} and {kwargs}")
        result = func(*args, **kwargs)
        print(f"Function {func.__name__} returned {result}")
        return result
    return wrapper

@log_decorator
def add(a, b):
    return a + b

add(2, 3)

Thus, a decorator provides a convenient way to add additional behavior to functions or methods, such as logging, access rights checking, caching, etc.