4.11. 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)

4.11.1. SetUp

>>> from dataclasses import dataclass

4.11.2. 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

4.11.3. 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

4.11.4. 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