Decorators with arguments
Another previously discussed snippet showed that decorators can accept arguments:
def warehouse_decorator(material):
def wrapper(our_function):
def internal_wrapper(*args):
print('* Wrapping items from {} with {}'.format(our_function.__name__, material))
our_function(*args)
print()
return internal_wrapper
return wrapper
@warehouse_decorator('kraft')
def pack_books(*args):
print("We'll pack books:", args)
And this code could be transcribed to a decorator expressed as a class, presented in the right pane.
When you pass arguments to the decorator, the decorator mechanism behaves quite differently than presented in example of decorator that does not accept arguments (previous slide):
- the reference to function to be decorated is passed to
__call__method which is called only once during decoration process, - the decorator arguments are passed to
__init__method
Code
class WarehouseDecorator:def __init__(self, material):
self.material = material
def __call__(self, own_function):
def internal_wrapper(*args, **kwargs):
print('<strong>*</strong> Wrapping items from {} with {}'.format(own_function.__name__, self.material))
own_function(*args, **kwargs)
print()
return internal_wrapper
@WarehouseDecorator('kraft')
def pack_books(*args):
print("We'll pack books:", args)
@WarehouseDecorator('foil')
def pack_toys(*args):
print("We'll pack toys:", args)
@WarehouseDecorator('cardboard')
def pack_fruits(*args):
print("We'll pack fruits:", args)
pack_books('Alice in Wonderland', 'Winnie the Pooh')
pack_toys('doll', 'car')
pack_fruits('plum', 'pear')
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