220 – Orderable dataclasses

By default, dataclass instances are not orderable:

from dataclasses import dataclass

@dataclass
class Task:
    priority: int
    description: str

Task(1, "task 1") < Task(2, "task 2")
# TypeError

Trying to compare two instances of the class Task raises a TypeError.

Set the parameter order=True in the dataclass decorator to make your dataclasses automatically orderable based on its attributes:

from dataclasses import dataclass, field

@dataclass(order=True)
class Task:
    priority: int
    description: str = field(compare=False)

Task(1, "task 1") < Task(2, "task 2")
# True

By setting order=True you can order instances of Task based on the attributes priority and description. By setting compare=False in field, you exclude description from the comparisons.