OOP & classes
Classes, instances, methods, dataclasses, and object-oriented design in Python.
Borg pattern shared state in Python
Implement the Borg pattern to share state across class instances by assigning a class-level dictionary to each instance's __dict__.
class Borg:
_shared_state = {}
def __init__(self):
self.__dict__ = Borg._shared_state
class ConfigManager(Borg):
def __init__(self):
super().__init__()
if not hasattr(self, "settings"):
self.settings = {}
def set(self, key, value):
self.settings[key] = va…Define an Enum for Status Codes in Python
Create a readable StatusCode enum with HTTP-style status values and iterate over its members using the standard library Enum class.
from enum import Enum
class StatusCode(Enum):
OK = 200
CREATED = 201
BAD_REQUEST = 400
UNAUTHORIZED = 401
NOT_FOUND = 404
INTERNAL_ERROR = 500
if __name__ == "__main__":
code = StatusCode.NOT_FOUND
print(f"Name: {code.name}")
print(f"Value: {code.value}")
print(f"Is it OK? {co…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 Create Static Methods in a Python Class
Shows how to define and call static methods inside a class using @staticmethod, with utility functions that don't need instance or class state.
class MathUtils:
"""Utility class demonstrating static methods."""
@staticmethod
def add(a, b):
"""Return the sum of two numbers."""
return a + b
@staticmethod
def multiply(a, b):
"""Return the product of two numbers."""
return a * b
@staticmethod
…How to Implement the State Pattern in Python
Implement the State design pattern in Python by delegating behavior to state objects, letting a media player change actions dynamically without if-else chains.
class State:
def play(self, player): pass
def pause(self, player): pass
def stop(self, player): pass
class PlayingState(State):
def play(self, player):
return "Already playing"
def pause(self, player):
player.state = PausedState()
return "Pausing playback"
def stop(self…How to Use __getstate__ and __setstate__ for Pickle in Python
Customize Python object serialization with the pickle __getstate__ and __setstate__ hooks to control exactly what data is stored and how it is restored.
import pickle
class Temperature:
def __init__(self, celsius):
self.celsius = celsius
def __getstate__(self):
"""Customize what gets pickled."""
state = self.__dict__.copy()
# Convert to Fahrenheit for storage (simulate transformation)
state['fahrenheit'] = (self.celsiu…Memento Pattern in Python: Save and Restore Object State
Implement the Memento design pattern to snapshot and restore an object's state, demonstrated with a text editor undo feature.
class TextEditor:
def __init__(self, text="", cursor_pos=0):
self.text = text
self.cursor_pos = cursor_pos
def type_text(self, new_text):
self.text += new_text
self.cursor_pos += len(new_text)
def move_cursor(self, pos):
self.cursor_pos = max(0, min(pos, len(self.t…Browse by section
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OOP & classes — Python code examples
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