Data Classes in Python | Set 4 (Inheritance)

from dataclasses import dataclass


@dataclass
class Article:
    
    title: str
    content: str
    author: str


@dataclass
class GfgArticle(Article):
    
    language: str
    author: str
    upvotes: int = 0

1. Article is subclassed by GfgArticle
2. Both SuperClass and SubClass are DataClasses - although super-class or sub-class being a normal class is also possible. When a DataClass inherits a normal class, the __init__() from the super-class is overridden in sub-class.
3. author in GfgArticle overrides the same in Article - As the basic concept of inheritance, the value for its assignment is first looked in the sub-class and followed up the tree in super-class.

• If __init__() is not explicitly provided, the default __init__() expects attributes of super-class (Article) followed by attributes of sub-class as parameters.

GfgArticle(title: str, content: str, author: str, language: str, upvotes: int = 0)

Note: The signature expects author before language in-spite of opposite order of declaration in GfgArticle. This comes from the fact that attributes are scanned top to bottom from super-class followed by sub-class. So author is first scanned in Article then language is scanned in GfgArticle. Python3 1==

dClassObj = GfgArticle("DataClass",
                       "SuperCool DataStructure",
                       "vibhu4agarwal",
                       "Python3")
print(dClassObj)

Output:

GfgArticle(title='DataClass', content='SuperCool DataStructure', author='vibhu4agarwal', language='Python3', upvotes=0)

• If __init__() is explicitly provided, it should somehow initialize all it's own attributes as well as those in the super-class (Article).
Python3 1==

from dataclasses import dataclass


@dataclass
class Article:
    title: str
    content: str
    author: str


@dataclass(init = False)
class GfgArticle(Article):

    language: str
    author: str
    upvotes: int = 0

    def __init__(self, title):
        self.title = title
        self.language = "Python3"
        self.author = "vibhu4agarwal"
        self.content = "Inheritance Concepts"


dClassObj = GfgArticle("DataClass")
print(dClassObj)

GfgArticle(title='DataClass', content='Inheritance Concepts', author='vibhu4agarwal', language='Python3', upvotes=0)

• Parameters requirement in __init__() can be adjusted according to the need as long as it has some way of initializing all the attributes.
• Order of initialization doesn't matter. language is initialized before author, while content is initialized at last and it still works.