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.

Note

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)