dataclasses¶
dataclasses were introduced in Python 3.7 and are a special shortcut with which we can create classes that store data. Python offers a special decorator if we want to create such a class.
Tip
For table data I generally use pandas Series or DataFrames and if I need to store matrices with numbers I use Numpy.
Let’s say we want to store a class that represents an item with summary,
owner, state and id. We can define such a class with:
>>> from dataclasses import dataclass
>>> @dataclass
... class Item:
... summary: str = None
... owner: str = None
... state: str = "todo"
... id: int = None
...
The @dataclass decorator creates the __init__ and __repr__ methods.
If I display the instance of the class, I get the class name and the attributes:
>>> i1
Item(summary='My first item', owner='veit', state='todo', id=1)
In general, data classes are used as syntactic sugar for creating classes that store data. You can add extra functionality to your classes by defining methods. We will add a method to the class that creates an Item object from a Dict:
>>> @dataclass
... class Item:
... ...
... @classmethod
... def from_dict(cls, d):
... return Item(**d)
...
>>> item_dict = {
... "summary": "My first item",
... "owner": "veit",
... "state": "todo",
... "id": 1,
... }
>>> Item.from_dict(item_dict)
Item(summary='My first item', owner='veit', state='todo', id=1)