dataclassabc 0.0.12

A Python library that allows you to define abstract properties for dataclasses, bridging the gap between abstract base classes (ABCs) and dataclasses.

Dataclass-abc

A Python library that allows you to define abstract properties for dataclasses, bridging the gap between abstract base classes (ABCs) and dataclasses.

Installation

You can install dataclass-abc using pip:

pip install dataclassabc

Usage

The dataclassabc decorator enables the use of abstract properties within dataclasses. It resolves abstract properties defined in an abstract base class (ABC) and enforces their implementation through fields in the derived dataclass.

Example

Here's how you can define an abstract property in a base class and implement it in a derived dataclass:

from abc import ABC, abstractmethod

from dataclassabc import dataclassabc

# Define an abstract base class with an abstract property
class A(ABC):
    @property
    @abstractmethod
    def name(self) -> str: ...

# Use the dataclassabc decorator to implement the abstract property in a dataclass
@dataclassabc(frozen=True)
class B(A):
    # Implementing the abstract property 'name'
    name: str

Using the standard dataclass decorator from the dataclasses module to implement abstract properties will result in a TypeError, as shown below:

from abc import ABC, abstractmethod

from dataclasses import dataclass

@dataclass(frozen=True)
class B(A):
    name: str

# TypeError: Can't instantiate abstract class B without an implementation for abstract method 'name'
b = B(name='A')

Define mutable variables

You can define mutable abstract properties by using the @property and @name.setter decorators in the abstract class. The following example demonstrates how to define and set a mutable property:

Example

from abc import ABC, abstractmethod

from dataclassabc import dataclassabc

class A(ABC):
    @property
    @abstractmethod
    def name(self) -> str: ...

    @name.setter
    @abstractmethod
    def name(self, val: str): ...

@dataclassabc
class B(A):
    name: str

b = B(name='A')
# modify the mutable variable
b.name = 'B'

# Output will be b=B(name='B')
print(f'{b=}')