OOP & classes
Classes, instances, methods, dataclasses, and object-oriented design in Python.
Compute Derived Fields with @dataclass __post_init__ in Python
Compute derived fields like distance, area, and perimeter automatically in Python dataclasses using __post_init__ and field(init=False).
from dataclasses import dataclass, field
from math import sqrt
@dataclass
class Point:
x: float
y: float
distance: float = field(init=False)
def __post_init__(self):
self.distance = sqrt(self.x ** 2 + self.y ** 2)
@dataclass
class Rectangle:
width: float
height: float
area: flo…How to Validate User Input with a Dataclass in Python
A dataclass stores name, age, and email, and a validator class checks each field, returning a dictionary of boolean results.
from dataclasses import dataclass
@dataclass
class UserInput:
name: str
age: int
email: str
def is_valid_name(self) -> bool:
return bool(self.name.strip()) and len(self.name.strip()) >= 2
def is_valid_age(self) -> bool:
return isinstance(self.age, int) and 0 < self.age < 150
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OOP & classes — Python code examples
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