From the dataclasses.field docs: The parameters to field() are: default_factory: If provided, it must be a zero-argument callable that will be called when a default value is needed for this field. Among other purposes, this can be used to specify fields with mutable default values, as discussed below. It is an error to specify both … Read more
From the docs: Here are the rules governing implicit creation of a __hash__() method: […] If eq and frozen are both true, by default dataclass() will generate a __hash__() method for you. If eq is true and frozen is false, __hash__() will be set to None, marking it unhashable (which it is, since it is … Read more
Much like you can add support to the JSON encoder for datetime objects or Decimals, you can also provide a custom encoder subclass to serialize dataclasses: import dataclasses, json class EnhancedJSONEncoder(json.JSONEncoder): def default(self, o): if dataclasses.is_dataclass(o): return dataclasses.asdict(o) return super().default(o) json.dumps(foo, cls=EnhancedJSONEncoder)
I’m the author of dacite – the tool that simplifies creation of data classes from dictionaries. This library has only one function from_dict – this is a quick example of usage: from dataclasses import dataclass from dacite import from_dict @dataclass class User: name: str age: int is_active: bool data = { ‘name’: ‘john’, ‘age’: 30, … Read more
Disclaimer: It seems that several people are concerned about presenting this solution, so I will provide a very clear disclaimer. You should not use this solution. I only provide it as information, so you know that the language is capable of this. The rest of the answer is just showing language capabilities, not endorsing using … Read more
It depends on your needs. Each of them has own benefits. Here is a good explanation of Dataclasses on PyCon 2018 Raymond Hettinger – Dataclasses: The code generator to end all code generators In Dataclass all implementation is written in Python, whereas in NamedTuple, all of these behaviors come for free because NamedTuple inherits from … Read more
The prefered Syntax for a typed named tuple since 3.6 is from typing import NamedTuple class Point(NamedTuple): x: int y: int = 1 # Set default value Point(3) # -> Point(x=3, y=1) Edit Starting Python 3.7, consider using dataclasses (your IDE may not yet support them for static type checking): from dataclasses import dataclass @dataclass … Read more
The way dataclasses combines attributes prevents you from being able to use attributes with defaults in a base class and then use attributes without a default (positional attributes) in a subclass. That’s because the attributes are combined by starting from the bottom of the MRO, and building up an ordered list of the attributes in … Read more
Data classes are just regular classes that are geared towards storing state, rather than containing a lot of logic. Every time you create a class that mostly consists of attributes, you make a data class. What the dataclasses module does is to make it easier to create data classes. It takes care of a lot … Read more