OOP & classes
Classes, instances, methods, dataclasses, and object-oriented design in Python.
Python Adapter Class: Wrap Legacy Interface
Convert a legacy system's interface into a modern one using the Adapter pattern in Python, translating method calls and data formats.
class LegacySystem:
"""Legacy interface - old method names and parameter format."""
def query_employee_info(self, emp_id, emp_name):
return f"Legacy: {emp_id} - {emp_name}"
def update_employee_department(self, emp_id, department_code):
return f"Legacy: Updated {emp_id} to dept {department_…Unit of Work Pattern: Track Changes, Commit, and Rollback in Python
This code defines a UnitOfWork class that tracks operations (add) and supports commit to apply changes and rollback to revert them, using a dataclass-based logger.
from dataclasses import dataclass, field
from typing import Any, Callable, List, Tuple
@dataclass
class UnitOfWork:
log: List[Tuple[str, Callable, tuple, dict]] = field(default_factory=list)
def track(self, operation: str, fn: Callable, *args, **kwargs):
self.log.append((operation, fn, args, kwargs)…Validate dataclass fields with __post_init__ in Python
Add custom validation to a Python dataclass inside __post_init__, raising ValueError or TypeError for invalid field values.
from dataclasses import dataclass, field
from typing import Optional
@dataclass
class Product:
name: str
price: float
quantity: int = 1
category: Optional[str] = None
def __post_init__(self):
if not self.name or not isinstance(self.name, str):
raise ValueError("name must be a…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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