Python Cookbook

Read JSON File

Load and parse JSON from disk with error handling.

Write JSON File

Serialize Python objects to formatted JSON.

Read CSV with Pandas

Load CSV into a DataFrame with type inference.

Merge DataFrames

Join two DataFrames on a shared key.

GroupBy Aggregate

Summarize data by category with groupby.

Handle Missing Data

Fill or drop NaN values in datasets.

Parallel HTTP Downloads

Fetch multiple URLs concurrently with asyncio.

Retry HTTP Requests

Retry failed API calls with exponential backoff.

Parse HTML

Extract text and links from HTML with BeautifulSoup.

Send Email via SMTP

Send plain-text email with smtplib.

Watch File Changes

React to filesystem events with watchdog.

Compress Files

Create zip archives programmatically.

Hash Password

Securely hash passwords with bcrypt.

Generate Secure Token

Create URL-safe random tokens.

Parse Datetime Strings

Convert date strings to datetime objects.

Timezone Conversion

Convert timestamps between timezones.

Read Environment Variables

Load config from environment with defaults.

Load .env File

Load local environment variables from .env.

SQLite CRUD

Basic create-read-update-delete with sqlite3.

SQLAlchemy Session

Query ORM models with a session.

FastAPI Endpoint

Create a typed JSON API endpoint.

Flask Blueprint

Organize routes with blueprints.

Django Management Command

Create a custom manage.py command.

Pytest Fixture

Share test setup with fixtures.

Mock External API

Patch HTTP calls in unit tests.

Rotating Log Files

Configure logs that rotate by size.

Click CLI

Build a command-line interface with Click.

Argparse CLI

Parse command-line arguments with argparse.

Read YAML Config

Load YAML configuration files safely.

Validate with Pydantic

Validate data models at runtime.

LRU Cache

Memoize expensive function calls.

Profile Code

Find bottlenecks with cProfile.

Multiprocessing Pool

Parallelize CPU work across processes.

Thread Pool for I/O

Run blocking I/O concurrently.

Redis Cache

Cache API responses in Redis.

Celery Background Task

Offload work to a background worker.

Schedule Jobs

Run functions on a schedule.

WebSocket Client

Connect to a WebSocket server.

Plot with Matplotlib

Create a line chart from data.

Plot with Seaborn

Statistical visualization with Seaborn.

Train Scikit-learn Model

Fit a classifier on tabular data.

Save ML Model

Persist trained models with joblib.

Load CSV (stdlib)

Read CSV without third-party deps.

Walk Directory Tree

Recursively list files in a folder.

Pathlib Operations

Modern path manipulation with pathlib.

Run Shell Command

Execute external commands safely.

Temporary File

Create auto-cleaned temp files.

Copy Directory Tree

Duplicate a folder recursively.

Glob File Patterns

Find files matching patterns.

Regex Extract

Pull patterns from text with re.

Dataclass Model

Define data containers with dataclasses.

Enum Constants

Define named constants with Enum.

Custom Context Manager

Manage resources with contextlib.

Custom Iterator

Build iterable objects with iter.

Logging Decorator

Log function entry and exit.

Singleton Pattern

Ensure one instance of a class.

Rate Limit API

Simple in-memory rate limiter.

Decode JWT

Verify and decode JSON Web Tokens.

Upload to S3

Upload files to AWS S3 with boto3.

AWS Lambda Handler

Minimal Lambda function handler.

Docker Healthcheck

Add health check to Dockerfile.

GitHub API

Fetch repo info from GitHub API.

Pivot Table

Create pivot tables from DataFrames.

NumPy Linear Algebra

Solve linear systems with NumPy.

Filter List

Filter elements with list comprehension.

Dict get Default

Safe dictionary access patterns.

Custom Sort Key

Sort objects by attribute.

Chunk a List

Split a list into fixed-size batches.

Flatten Nested List

Flatten one level of nesting.

Count Words

Count word frequency in text.

Slugify String

Convert title to URL slug.

Parse URL

Extract components from URLs.

Base64 Encode

Encode binary data as base64.

HMAC Signature

Sign payloads with HMAC-SHA256.

Read Excel

Load Excel sheets into Pandas.

Write Parquet

Save DataFrame as Parquet for analytics.

API Pagination

Fetch all pages from a paginated API.

WebSocket Broadcast

Broadcast message to all clients.

SQL Injection Safe Query

Use parameterized SQL queries.

Write CSV Dict

Write rows from dicts to CSV.

Parse XML

Parse XML with ElementTree.

Read INI Config

Load .ini configuration files.

Read TOML Config

Load TOML with tomllib (3.11+).

Type Narrowing

Narrow types with isinstance checks.

Generic Function

Write type-safe generic functions.

Async Gather

Run coroutines concurrently.

Async Queue

Producer-consumer with asyncio.Queue.

Signal Handler

Handle SIGINT/SIGTERM gracefully.

Daemon Thread

Run background thread that exits with main.

Thread-Safe Queue

Share work between threads safely.

Property Validation

Validate attributes with @property.

Abstract Base Class

Define interfaces with ABC.

Readable repr

Implement repr for debugging.

Stream Large CSV

Process large CSV row by row.

Memory Usage

Track object memory with sys.getsizeof.

Force Garbage Collection

Manually trigger garbage collection.

Weakref Cache

Cache without preventing GC.

Parse IP Address

Validate and inspect IP addresses.

Generate UUID

Create unique identifiers.

Decimal for Money

Avoid float errors with Decimal.

Exact Fractions

Represent rationals exactly.