Data classes

pep 557

Mutable namedtuple with defaults and support annotation

Note

Read mamedtuple first

from dataclasses import dataclass
from typing import Tuple

@dataclass( init=True, repr=True, eq=True, order=False, unsafe_hash=False, frozen=False, match_args=True, kw_only=False, slots=False, weakref_slot=False)
class InventoryItem:
    '''Class for keeping track of an item in inventory.'''
    name: str
    unit_price: float
    quantity_on_hand: int = 0

    def total_cost(self) -> float:
        return self.unit_price * self.quantity_on_hand

The @dataclass decorator will add the equivalent of these methods to the InventoryItem class:

def __init__(self, name: str, unit_price: float, quantity_on_hand: int = 0) -> None:
    self.name = name
    self.unit_price = unit_price
    self.quantity_on_hand = quantity_on_hand
def __repr__(self):
    return f'InventoryItem(name={self.name!r}, unit_price={self.unit_price!r}, quantity_on_hand={self.quantity_on_hand!r})'
def __eq__(self, other):
    if other.__class__ is self.__class__:
        return (self.name, self.unit_price, self.quantity_on_hand) == (other.name, other.unit_price, other.quantity_on_hand)
    return NotImplemented
def __ne__(self, other):
    if other.__class__ is self.__class__:
        return (self.name, self.unit_price, self.quantity_on_hand) != (other.name, other.unit_price, other.quantity_on_hand)
    return NotImplemented
def __lt__(self, other):
    if other.__class__ is self.__class__:
        return (self.name, self.unit_price, self.quantity_on_hand) < (other.name, other.unit_price, other.quantity_on_hand)
    return NotImplemented
def __le__(self, other):
    if other.__class__ is self.__class__:
        return (self.name, self.unit_price, self.quantity_on_hand) <= (other.name, other.unit_price, other.quantity_on_hand)
    return NotImplemented
def __gt__(self, other):
    if other.__class__ is self.__class__:
        return (self.name, self.unit_price, self.quantity_on_hand) > (other.name, other.unit_price, other.quantity_on_hand)
    return NotImplemented
def __ge__(self, other):
    if other.__class__ is self.__class__:
        return (self.name, self.unit_price, self.quantity_on_hand) >= (other.name, other.unit_price, other.quantity_on_hand)
    return NotImplemented