A plain wrapper hides the original function's name and docstring, which confuses debugging tools and help():

from functools import wraps

def plain(func):
    def wrapper(*args, **kwargs):
        return func(*args, **kwargs)
    return wrapper

def proper(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
        return func(*args, **kwargs)
    return wrapper

@plain
def one():
    """The first function."""

@proper
def two():
    """The second function."""

print(one.__name__, one.__doc__)
print(two.__name__, two.__doc__)

@wraps(func) copies the name, docstring and other details onto the wrapper. Always use it in decorators you write.