Python Decorator with Optional Keyword Arguments

opt_decorator.py

"""
Function decorator with optional keyword arguments.
"""

from functools import wraps

def decorate(func=None, kind=''):
    if func is None:
        # was called pre-decoration.  Return anonymous decorator.
        return lambda f: decorate(f, kind)

    # Normal case: decorate passed function.
    @wraps(func)
    def wrapper(*args, **kwargs):
        return f'{kind}wrapped ' + func(*args, **kwargs)
    return wrapper


# Decorate function with default options..
@decorate
def foo(arg):
    """This is foo."""
    return f'foo(arg={arg})'

result = foo(3)
assert result == 'wrapped foo(arg=3)'
assert foo.__name__ == 'foo'
assert foo.__doc__ == 'This is foo.'


# Decorate function with changed option.
@decorate(kind='gift ')
def bar(arg):
    """This is bar."""
    return f'bar(arg={arg})'

result = bar(3)
assert result == 'gift wrapped bar(arg=3)'
assert bar.__name__ == 'bar'
assert bar.__doc__ == 'This is bar.'