Flask .gitignore template

instance is the rule that makes this template worth adding on top of Python. The framework supports an instance folder that sits outside the package and holds anything specific to this deployment: the configuration file with the secret key and database URL, a SQLite file, uploaded content. The framework knows how to load configuration from it, and the convention is that it is never committed.

That convention is more useful than it first looks, because it gives you one directory to ignore instead of a list of individual files. A project that keeps its config in instance/config.py has a single rule protecting it, and a new developer who sees an empty instance folder understands immediately that something is expected there.

.webassets-cache is the cache directory used by the asset bundling extension, holding compiled and merged stylesheets and scripts keyed by content. It is regenerated on demand and specific to one machine's filesystem layout. Committing it produces a cache that never hits, because the keys were computed against paths that do not exist on the machine reading them.

The Python rules underneath cover bytecode, virtual environments, packaging output and the test caches: __pycache__, *.pyc, venv, .venv, dist, build, *.egg-info, htmlcov, .tox, .coverage and .pytest_cache. That is a smaller set than the standalone Python template, so pairing the two is still worthwhile if you use type checking or linting caches.

The .env rule matters here for the same reason it does everywhere in this ecosystem: the convention is to load configuration from the environment, and in development that environment comes from a file on disk holding the real database URL and the real API keys.