Python Code
Samples
Copy-ready Python snippets by topic and difficulty — short, focused, and runnable in the browser editor.
How to Mock and Test a Rate-Limited Source Stream in Python
Build a class that rate-limits emitted items using a sliding window and test it with a simulated stream in Python.
import time
from collections import deque
class RateLimitedSource:
def __init__(self, max_rate, window=1.0):
self.max_rate = max_rate
self.window = window
self._timestamps = deque()
def emit(self, item):
now = time.monotonic()
while self._timestamps and self._timestam…How to implement a tumbling window aggregation in Python
Build a mock tumbling window aggregator in Python that groups streaming events into fixed time intervals and computes count, sum, and average per window.
import time
from collections import deque
class TumblingWindow:
def __init__(self, duration_seconds):
self.duration = duration_seconds
self.buffer = deque()
self.window_start = None
def add(self, item):
current_time = time.time()
if self.window_start is None:
…How to select specific columns in Python with SQLite
A reusable function that connects to a SQLite database and returns only the requested columns from a given table.
import sqlite3
def select_pruned_columns(db_path, table, columns):
with sqlite3.connect(db_path) as conn:
cursor = conn.cursor()
col_list = ", ".join(columns)
query = f"SELECT {col_list} FROM {table}"
return cursor.execute(query).fetchall()
if __name__ == "__main__":
conn = sq…How to Create a Mock Metaflow Flow in Python
Build a minimal Metaflow flow with two sequential steps that pass data between them using instance attributes.
from metaflow import FlowSpec, step, current
class MockFlow(FlowSpec):
"""A minimal Metaflow flow to demonstrate basic steps and branching."""
@step
def start(self):
self.category = "mock"
print(f"Start step for {self.category} flow")
self.next(self.process)
@step
def pr…How to Mock Sequential Calls in Python with unittest.mock
Use Mock.side_effect to return a different result for each sequential call and verify the call order with assert_has_calls.
import unittest
from unittest.mock import Mock
class Service:
def fetch(self, item_id):
raise NotImplementedError
def process_items(service, ids):
results = []
for item_id in ids:
result = service.fetch(item_id)
results.append(result)
return results
if __name__ == "__main__":…How to Perform Welch's t-Test in Python
Calculate the Welch t-statistic and degrees of freedom for two samples with unequal variances using Python's statistics module.
import math
from statistics import mean, variance
def welch_t_test(sample1, sample2):
n1, n2 = len(sample1), len(sample2)
mean1, mean2 = mean(sample1), mean(sample2)
var1, var2 = variance(sample1), variance(sample2)
# Welch's t statistic
t_stat = (mean1 - mean2) / math.sqrt(var1 / n1 + var2 / n2…Hash index equality mock concept in Python
A simple hash index class in Python that stores key-value pairs in buckets and demonstrates basic equality-based lookup.
class HashIndex:
def __init__(self):
self._buckets = {}
def insert(self, key, value):
"""Insert a key-value pair into the hash index."""
index = hash(key) % 10
if index not in self._buckets:
self._buckets[index] = []
self._buckets[index].append((key, value))…How to Validate Data Before Scaling in Python
A reusable Python helper that validates required fields and constraint checks on data rows before entering a database pipeline, improving data quality and throughput.
def validate_data(data, required_fields, constraints=None):
"""
Basic validation helper demonstrating data-quality workflows
before scaling (catches bad rows early, improves throughput).
"""
constraints = constraints or {}
errors = []
for field in required_fields:
if field not in d…Idempotent Writes for Sharded Databases in Python
Implement a mock shard with idempotent write support using request IDs to prevent duplicate writes and track the latest value per key.
import json
class ShardMock:
"""Mock distributed shard with idempotent write support."""
def __init__(self, shard_id):
self.shard_id = shard_id
self._store = {}
def write(self, key, value, request_id):
"""Write value only if request_id not yet processed; idempotent."""
i…UUID vs sequential primary key in Python
Simulate and compare UUID vs sequential primary key generation in Python to understand trade-offs in ordering and uniqueness.
import uuid
import time
def create_record_with_uuid(name):
record_id = uuid.uuid4()
return {"id": record_id, "name": name}
def create_record_with_sequential_id(name, counter):
counter += 1
return {"id": counter, "name": name}
if __name__ == "__main__":
# Simulate users inserting records
sequ…How to Create and Verify HMAC SHA256 API Signatures in Python
Generate and verify HMAC-SHA256 signatures for API requests using Python's hmac, hashlib, and base64 modules.
import hmac
import hashlib
import base64
import json
from datetime import datetime, timezone
def create_api_signature(secret_key: str, method: str, path: str, timestamp: str, body: dict = None) -> str:
"""Create HMAC-SHA256 signature for API request."""
payload = {
"method": method.upper(),
"p…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 Build a Data Helper for Production Deployment in Python
Build a reusable DataHelper class that loads configs, validates required keys, normalizes string values, and logs schema details — a production-ready data processing pattern.
import json
from pathlib import Path
from typing import Any, Dict
class DataHelper:
"""Common data processing patterns for production deployment."""
def __init__(self, config_path: str | Path):
self.config_path = Path(config_path)
self.config = self._load_config()
def _load_confi…How to Deploy Staging Then Production in Python
Walk through a staged deployment mock that promotes from staging to production in sequence with Python.
import time
def deploy_environment(name: str) -> None:
print(f"Deploying to {name}...")
time.sleep(0.1)
print(f"Deployed to {name} ✔")
def deploy_staging_then_prod() -> None:
environments = ["staging", "production"]
for env in environments:
deploy_environment(env)
if env == "stagi…How to Mock Canary Deployment Traffic Split in Python
Simulate a canary deployment's stable/canary traffic split using deterministic request hashing to mock rollout behavior with precise percentage control.
class CanaryDeployment:
def __init__(self, stable_weight: float = 0.9, canary_weight: float = 0.1):
self.stable_weight = stable_weight
self.canary_weight = canary_weight
self.total_weight = stable_weight + canary_weight
def route_request(self, request_id: int) -> str:
"""Route …How to mock resource request limits in Python
A Python class that simulates CPU and memory limit checks for resource requests, returning clear acceptance or rejection messages.
class ResourceLimits:
def __init__(self, cpu_limit, memory_limit):
self.cpu_limit = cpu_limit
self.memory_limit = memory_limit
def check_request(self, cpu, memory):
if cpu > self.cpu_limit:
return "CPU limit exceeded: {cpu} > {limit}".format(cpu=cpu, limit=self.cpu_limit)
…How to simulate GitLab CI stages in Python
Build a lightweight Python mock of GitLab CI pipeline stages to test job sequencing and output locally.
def mock_gitlab_ci_stages():
stages = ["build", "test", "deploy"]
stage_status = {}
for stage in stages:
jobs = []
if stage == "build":
jobs = ["compile", "package"]
elif stage == "test":
jobs = ["unit", "integration", "e2e"]
elif stage == "deploy":…How to simulate a Jenkins pipeline in Python
Simulate a Jenkins-style pipeline in Python by running sequential stages and checking aggregate success.
def run_stage(name, duration, fn):
print(f"[Pipeline] Running stage: {name}")
result = fn()
print(f"[Pipeline] Stage '{name}' completed in {duration}s -> {result}")
return result
def build_project():
print(" compiling source...")
return "BUILD_OK"
def run_tests():
print(" executing unit…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.