4.10. Dataclass Inheritance

Dataclasses can inherit from other classes
Superclass not necessarily has to be dataclass
If parent is dataclass the init will be joined (all parameters from parent and child will be set)

4.10.1. SetUp

>>> from dataclasses import dataclass

4.10.2. Inheritance

>>> @dataclass
... class Account:
...     firstname: str
...     lastname: str
>>>
>>>
>>> @dataclass
... class User(Account):
...     role: str = 'user'

Will generate:

>>> class User:
...     firstname: str
...     lastname: str
...     role: str = 'user'
...
...     def __init__(self,
...                  firstname: str,
...                  lastname: str,
...                  role: str = 'user'):
...
...         self.firstname = firstname
...         self.lastname = lastname
...         self.role = role

4.10.3. Post Init

When a child class define __post_init__() method it will overwrite this method from a parent class:

>>> @dataclass
... class Account:
...     firstname: str
...     lastname: str
...
...     def __post_init__(self):
...         print('Account post init')
>>>
>>>
>>> @dataclass
... class User(Account):
...     role: str = 'user'
...
...     def __post_init__(self):
...         print('User post init')
>>>
>>>
>>> mark = User('Mark', 'Watney')
User post init

4.10.4. Super

Using super() allows a child class to call __post_init__() from a superclass. Note that all the parameters are already assigned, no need to pass them like for __init__() function.

>>> @dataclass
... class Account:
...     firstname: str
...     lastname: str
...
...     def __post_init__(self):
...         print('Account post init')
>>>
>>>
>>> @dataclass
... class User(Account):
...     role: str = 'user'
...
...     def __post_init__(self):
...         super().__post_init__()
...         print('User post init')
>>>
>>>
>>> mark = User('Mark', 'Watney')
Account post init
User post init