Menu
Do dataclasses have a way to add additional initialization aside from what is provided with its built in initializer, without overriding it? Specifically, I want to check some values of a list of integers that is one of the fields in the data class upon initialization.
220
A Python class is a program used to create objects and their properties. We use the keyword class to create a class in Python. For class attributes to be initialized, we use a constructor method called __init__() which is called when an object is created in a Python class.
Modifying fields after initialization with __post_init__ The __post_init__ method is called just after initialization. In other words, it is called after the object receives values for its fields, such as name , continent , population , and official_lang .
A dataclass can very well have regular instance and class methods. Dataclasses were introduced from Python version 3.7. For Python versions below 3.7, it has to be installed as a library.
Here is the same Python class, implemented as a Python dataclass: When you specify properties, called fields, in a dataclass, @dataclass automatically generates all of the code needed to initialize them.
How to use Python dataclasses 1 Python dataclass example. ... 2 Customize Python dataclass fields with the field function. ... 3 Use __post_init__ to control Python dataclass initialization. ... 4 Use InitVar to control Python dataclass initialization. ... 5 When to use Python dataclasses — and when not to use them. ...
The default way dataclasses work should be okay for the majority of use cases. Sometimes, though, you need to fine-tune how the fields in your dataclass are initialized. To do this, you can use the field function. When you set a default value to an instance of field, it changes how the field is set up depending on what parameters you give field.
A data class is a class typically containing mainly data, although there aren’t really any restrictions. It is created using the new @dataclass decorator, as follows: from dataclasses import dataclass @dataclass class DataClassCard: rank: str suit: str
As described in the dataclass PEP, there is a __post_init__ method, which will be the last thing called by __init__.
from dataclasses import dataclass
@dataclass
class DataClass:
some_field: int
def __post_init__(self):
print(f"My field is {self.some_field}")
Defining this dataclass class, and then running the following:
dc = DataClass(1) # Prints "My field is 1"
Would initialize some_field to 1, and then run __post_init__, printing My field is 1.
This allows you to run code after the initialization method to do any additional setup/checks you might want to perform.
125
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With