Uniquorn

A Python metaclass to create class instances with the same parameters only once.

Sometimes you need to avoid duplicated class instances with the same parameters. The Uniquorn metaclass makes this easy.

Basic usage

To avoid creating multiple instances with the same instantiation parameters simply designate Uniquorn as your class' metaclass.

from uniquorn import Uniquorn

class ExampleClass(metaclass=Uniquorn):

    def __init__(self, ...):
        ...

List and dict order

By default, the order of items in list and dict parameters is irrelevant to Uniquorn. It sorts the items in an attempt to detect duplicates.

You can tell Uniquorn the order of items is relevant to your class through uniquorn_list_order_matters and uniquorn_dict_order_matters. By assigning True you tell Uniquorn for that type of parameter the order of the items is relevant. Alternatively, you can assign the names of the parameters as a list, tuple or set to tell Uniquorn for those parameters the order of the items is relevant.

from uniquorn import Uniquorn

class ExampleClass(metaclass=Uniquorn):

    uniquorn_list_order_matters = True
    uniquorn_dict_order_matters = ("param1", "param2", )

    def __init__(self, ...):
        ...

Limitations

• If you change the parameters after instance creation it will not be noted by Uniquorn.
• Apart from the mechanism described under 'List and dict order' above, Uniquorn makes no attempt to match parameters based on their internal structure.