Python Code
Samples
Copy-ready Python snippets by topic and difficulty — short, focused, and runnable in the browser editor.
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)…Rollback dataset to previous snapshot pointer in Python
A SnapshotManager class stores timestamped data snapshots and rolls back to the most recent snapshot at or before a target time.
from datetime import datetime, timedelta
class SnapshotManager:
def __init__(self):
self.snapshots = {} # timestamp -> data
self.current_pointer = None
def create_snapshot(self, data):
timestamp = datetime.now()
self.snapshots[timestamp] = data
self.current_pointer =…Mock Unit of Work commit and rollback in Python
Verify that a Unit of Work pattern commits on success and rolls back on failure using unittest.mock in Python.
from unittest import mock
class UnitOfWork:
def __init__(self):
self.committed = False
self.rolled_back = False
def commit(self):
self.committed = True
print("Commit executed")
def rollback(self):
self.rolled_back = True
print("Rollback executed")
def b…Saga pattern orchestration with rollback in Python
Orchestrate a distributed transaction with Saga steps and automated compensation rollback on failure.
import time
import random
class SagaStep:
def __init__(self, name):
self.name = name
self.executed = False
def execute(self):
print(f"Executing {self.name}...")
time.sleep(0.2)
if random.random() < 0.3:
raise RuntimeError(f"{self.name} failed")
sel…How to Simulate Distributed Transactions in Python with a Mock
Model distributed transaction behavior with a mock Transaction class that supports commit, rollback, and failure simulation.
class Transaction:
def __init__(self, id):
self.id = id
self.operations = []
self.committed = False
def add_operation(self, op, data):
self.operations.append((op, data))
def commit(self):
if not self.operations:
raise ValueError("No operations to commit…How to mock batch commit of transactions in Python
Simulate a transaction batch writer with commit, rollback, and summary logic to test database write patterns without a real database.
import json
from datetime import datetime, timezone
class TransactionBatch:
def __init__(self):
self.pending = []
self.committed = []
self._log = []
def add(self, operation):
self.pending.append(operation)
def commit(self):
if not self.pending:
return …Auto Rollback on Error Rate Exceeded in Python
Simulate a service that monitors a rolling window of request errors and automatically rolls back when the error rate exceeds a threshold.
import random
import time
def simulate_requests(total_requests=1000, rollback_threshold=0.2):
"""
Simulate a service that automatically rolls back when the error rate
exceeds a threshold within a rolling window.
"""
window_size = 100
errors_seen = []
rolled_back = False
for req_num i…How to Roll Back to a Previous Image Tag in Python
A dataclass-based mock registry that tracks image tag history and rolls back to the previous tag, useful for deployment rollback logic.
"""Demonstrates a rollback pattern for a Docker-style image tag registry."""
from dataclasses import dataclass, field
@dataclass
class ImageRegistry:
"""A minimal mock registry tracking current tags per image."""
tags: dict[str, list[str]] = field(default_factory=dict)
def push(self, image: str, tag: …How to Simulate Blue-Green Deployment Switch in Python
A mock Blue-Green deployment class that deploys new versions to an inactive environment, runs a health check, switches traffic, and supports rollback in Python.
import random
import time
class BlueGreenDeployment:
def __init__(self, initial_env="blue"):
self.environments = {"blue": "v1.0", "green": "v1.0"}
self.active_env = initial_env
self.running = True
def deploy_new_version(self, version, target_env):
if target_env == self.active_…Browse by section
Each section groups closely related Python snippets.
Guide: free Python code samples library
Copy-ready Python snippets for learners and developers
PythonSkillset code samples are short, focused examples organised by topic and difficulty. Every snippet is server-rendered HTML — readable by search engines and easy to copy. Open any sample, read the notes, copy the code, then press Try in editor to run it in the browser with Pyodide.
How to use this library
- Pick a topic section — strings, lists, files, functions, and more
- Open a sample, read How it works, and copy the code block
- Run it in the IDE, tweak values, then take a related quiz or tutorial lesson
Samples vs tutorials and challenges
Samples are quick reference — one concept per page. For step-by-step teaching, use our Python tutorials. To test yourself, try quizzes or coding challenges. Clean up style with the Python formatter.