The go-to resource for upgrading Python, Django, Flask, and your dependencies.
69 articles on upgrading Python, Django, Flask, and managing dependencies
Configure Uvicorn to handle up to 10,000 concurrent WebSocket connections in FastAPI applications. Covers multi-worker setup, system tuning (ulimit, sysctl), benchmarks showing 5ms p99 latency and 50k msg/s throughput on Python 3.13, verified with websocket-bench. Addresses common issues like connection refused and too many open files.
Resolve 'python: command not found' after installing Python 3.13 with asdf. Step-by-step guide covering shims, PATH, shell setup, and troubleshooting.
Flask 3.1 to 4.0 migration guide: Fix Werkzeug 3.0 routing breaking changes including new state machine router, custom converters part_isolating=False, strict_slashes fixes, SERVER_NAME host_matching, UTF-8 charset removal. Code examples, steps, verification for seamless upgrade.
Flask application factory pattern guide: create_app() vs global app instance. Use factory for testing, config/env separation, blueprints/extensions (80% production apps). Global for quick prototypes. Code examples, migration steps, pytest integration, circular import fixes. Flask 3.0+ best practices.
Flask tutorial: installation, hello world app, routes, Jinja templates, WTForms, SQLAlchemy ORM, Blueprints, deployment to Heroku/Vercel.
Flask-Login session fixation vuln: No auto session ID regen post-login → attacker hijacks via pre-auth session fixation (OWASP A5). Fix: session.regenerate() after login_user(). Code, audit, tests. Benchmarks: 0 vuln → secure.
Migrate your Flask-SQLAlchemy models from legacy db.Model to SQLAlchemy 2.0 declarative base syntax using Mapped and mapped_column. Fix post-upgrade TypeErrors, gain type hints and IDE support, ensure Alembic compatibility.
Flask vs FastAPI WebSocket benchmarks on Python 3.13 M2 Mac: compare latency and throughput for realtime apps. Includes code setups, py-spy analysis, uvicorn/gunicorn+SocketIO configs.
Configure Flask behind Nginx to preserve real client IP with X-Forwarded-For headers for GDPR logging. Covers Nginx proxy_set_header, Flask ProxyFix/werkzeug ProxyFix, Gunicorn --forwarded-allow-ips, Docker and Ubuntu setups.
Troubleshooting 422 Unprocessable Entity errors in FastAPI, caused by Pydantic validation failures in request bodies. Covers debugging techniques, common causes like type mismatches and missing fields, and practical solutions including optional fields, unions, validators, and error handling.
pytest flaky tests random order fix: pytest-randomly shuffles execution order + seeds random, exposes hidden deps. Install pip, demo failing suite, reproduce w/ --randomly-seed=12345, fix w/ autouse fixtures. CI: --randomly-seed=last. Benchmarks detect 80% hidden flakiness. Keywords: 'fix flaky pytest tests', 'pytest-randomly tutorial', 'pytest random order execution', 'pytest flaky random seed', 'detect order dependent tests pytest'.
Resolve ImportError: cannot import name 'escape' from 'jinja2' when upgrading to Flask 2.3. Step-by-step fixes, code examples, and best practices for Jinja2 compatibility.
PCI DSS compliance Python: Fix vulnerable dependencies in requirements.txt. Step-by-step guide using pip-audit, safety CLI, pip-tools/uv locking. Quarterly scans, exact pinning, hashes for Req 6.2.3 audits. Pass vulnerability scans – requirements.txt security best practices 2026.
Pin direct + transitive (indirect) dependencies in requirements.txt using pip-tools or uv pip-compile. Pass pip-audit, Safety CLI, Snyk scans with exact versions/hashes. Reproducible, secure Python builds without version drift.
py-spy Flask profiling no code changes: Attach to gunicorn PID, py-spy top reveals 90% CPU in slow endpoint loop, flamegraph.svg export. 5x speedup fixes. Benchmarks: 200req/s → 1000req/s. Keywords: 'profile flask app py-spy', 'flask performance without instrumentation', 'py-spy gunicorn flask', 'flask cpu profiler no decorators'.
FastAPI orjson integration: 40% faster JSON responses (28ms → 17ms p99 avg). Custom ORJSONResponse class, benchmarks uvicorn Python 3.13, 10k req/s load. Pydantic v2 auto-detects orjson. Keywords: fastapi orjson, fastapi json performance, reduce fastapi response time, python json optimization.
Step-by-step guide to installing the Python 3.13t free-threaded build using mise on macOS Sonoma (14) for Apple Silicon Macs.
Flask auth endpoint testing without DB: Mock Flask-Login user_loader, pytest fixtures for test_client + fake user. Parallel-safe (500 tests/s), zero flakes/DB setup. Full app+tests code. Keywords: 'flask test authentication endpoints no database', 'pytest flask-login mock user', 'flask test_client login without db'.
Verify PGP signatures Python packages pip: GPG check PyPI .asc files for cryptography requests wheels. Manual supply chain security beyond pip hashes. Step-by-step gpg --verify guide, key import, troubleshooting. PyPI package signature verification 2026.
Learn how to detect and fix memory leaks in Celery workers using Python's built-in tracemalloc module. Includes signal handlers for production and benchmarks showing RSS growth from 200MB to 2GB.
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