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 Build a Context Manager Class in Python
Create a reusable context manager class that opens and automatically closes resources using the with statement.
class FileResource:
def __init__(self, filename, mode='r'):
self.filename = filename
self.mode = mode
self.file = None
def __enter__(self):
self.file = open(self.filename, self.mode)
return self.file
def __exit__(self, exc_type, exc_value, traceback):
if se…How to Use StrEnum with auto() in Python
Define string-valued enum members automatically by using StrEnum with the auto() helper, making each member's value its own uppercase name.
from enum import StrEnum, auto
class Color(StrEnum):
RED = auto()
GREEN = auto()
BLUE = auto()
class Language(StrEnum):
PYTHON = auto()
JAVASCRIPT = auto()
RUST = auto()
print(list(Color))
print(list(Language))
print(Color.RED == "RED")
print(Language.PYTHON == "PYTHON")
print(f"Color: {Co…Browse by section
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OOP & classes — Python code examples
What you will find here
This page collects oop & classes snippets — short, copy-ready Python you can paste into our free online IDE and run without installing anything. Each sample includes a plain-English explanation and the full source code.
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