Extending Flask using the Flask Plugins API

How to develop Flask plugins

Transcript

1. Extending Flask using the Flask Plugins API
3. About One of the organizer of Python Mauritius Usergroup (pymug) / FlaskCon / PyCon Africa OpenSource https://www.compileralchemy.com or Qr 3
4. so, about handles twitter @osdotsystem https://fosstodon.org/@osdotsystem linkedin.com/in/appinv/ 4
5. Extending Flask using the Flask Plugins API 5
6. Why this talk? 6
7. encourage people to maintain Flask projects Pallets Eco 7
8. encourage people to write extensions give users SUPER powers improve Flask dev experience contributes to make Flask a compelling choice saves time 8
9. understand extensions the seed to muster the courage to dive into codebases 9
10. Approaches to plugins in Python 10
11. The auto-load method python ---> find packages start with fruit_ | V iterate find attributes 11
12. Plugins list method python ---> developers specify plugins | V load iterate find attributes 12
13. Plugin manager python ---> plugin manager | V find plugin load extract info pass back 13
14. Flask app = create_app() | app ---. | V .---------. | plugin1 | plugin1.init_app(app) .---------. | app <--. // modified | app ---. | V .---------. | plugin2 | plugin2.init_app(app) .---------. | app <--. // modified | 14
15. Order of plugins matter sometimes 15
16. Not always need to be named .init_app 16
17. Really? 17
18. Yes, docs says The most common pattern is to create a class that represents the extension’s configuration and behavior, with an init_app method to apply the extension instance to the given application instance. 18
19. Also The only time the extension should have direct access to an app is during init_app, otherwise it should use current_app. 19
20. class HelloExtension: def __init__(self, app=None): if app is not None: self.init_app(app) def init_app(self, app): app.before_request(...) 20
21. before_request(f) Register a function to run before each request. @app.before_request def load_user(): if "user_id" in session: g.user = db.session.get(session["user_id"]) # ... def init_app(self, app): app.before_request(greet_user) def greet_user(self): print('Welcome to FlaskCon') 21
22. So, building extensions is about 22
23. knowing Flask internals well ... 23
24. Useful tips 24
25. current_app g global variables, during request, per thread 25
26. Real app current_app._get_current_object() 26
27. blueprint also has cli.group 27
28. Common ideas 28
29. Configs -> Flask app config 29
30. flask-tabler-icons 30
31. from typing import Any from flask import Blueprint, Flask # version is same as tabler-icons __version__ = "3.3.0" class TablerIcons: def __init__(self, app: Any = None) -> None: if app is not None: self.init_app(app) def init_app(self, app: Flask) -> None: if not hasattr(app, "extensions"): app.extensions = {} app.extensions["tabler_icons"] = self bp = Blueprint( "tabler_icons", __name__, static_folder="static", static_url_path=f"/tabler-icons{app.static_url_path}", template_folder="templates", ) app.register_blueprint(bp) app.jinja_env.globals["tabler_icons"] = self app.config.setdefault("TABLER_ICON_SIZE", 24) 31
32. {% macro fill_css(value="", prefix="", yes_value="", postfix="") %} ... {% endmacro %} {% macro render_icon(icon, color="", bold=false, class="", style="", animation="", css_color="", size=0) %} {% if css_color %} {% set css_color = "color: %s;"|format(css_color) %} {% endif %} {% set bold = " font-weight: bold;" if bold else "" %} {% set animation_css = fill_css(animation, ' icon-') %} {% if color or class %} {% set class = "%s %s"|format(class, ("text-" + color) if color else "") %} {% endif %} <span {% if class %}class="{{ class }}"{% endif %} {% if css_color or bold or style %} style="{{ css_color }}{{ bold }} {{ style }}" {% endif %} > <svg class="icon-tabler{{ animation_css }}" width="{{ size or config.TABLER_ICON_SIZE}}" height="{{ size or config.TABLER_ICON_SIZE }}" > <use href="{{ url_for('tabler_icons.static', filename='tabler-sprite.svg') }}#tabler-{{ icon }}" /> </svg> </span> {% endmacro %} 32
33. static/tabler-icon.svg 33
34. flask-MonitoringDashboard 34
35. from flask import Flask import flask_monitoringdashboard as dashboard app = Flask(__name__) @app.route("/test") def test(): return 'ok' dashboard.bind(app) // here app.run() 35
36. Flask-sqlalchemy 36
37. def init_app(self, app: Flask) -> None: if "sqlalchemy" in app.extensions: raise RuntimeError( "A 'SQLAlchemy' instance has already been registered on this Flask app." " Import and use that instance instead." ) app.extensions["sqlalchemy"] = self app.teardown_appcontext(self._teardown_session) if self._add_models_to_shell: from .cli import add_models_to_shell app.shell_context_processor(add_models_to_shell) basic_uri: str | sa.engine.URL | None = app.config.setdefault( "SQLALCHEMY_DATABASE_URI", None ) basic_engine_options = self._engine_options.copy() basic_engine_options.update( app.config.setdefault("SQLALCHEMY_ENGINE_OPTIONS", {}) ) echo: bool = app.config.setdefault("SQLALCHEMY_ECHO", False) config_binds: dict[str | None, str | sa.engine.URL | dict[str, t.Any]] = ( app.config.setdefault("SQLALCHEMY_BINDS", {}) ) engine_options: dict[str | None, dict[str, t.Any]] = {} 37
38. # Build the engine config for each bind key. for key, value in config_binds.items(): engine_options[key] = self._engine_options.copy() if isinstance(value, (str, sa.engine.URL)): engine_options[key]["url"] = value else: engine_options[key].update(value) # Build the engine config for the default bind key. if basic_uri is not None: basic_engine_options["url"] = basic_uri if "url" in basic_engine_options: engine_options.setdefault(None, {}).update(basic_engine_options) if not engine_options: raise RuntimeError( "Either 'SQLALCHEMY_DATABASE_URI' or 'SQLALCHEMY_BINDS' must be set." ) 38
39. engines = self._app_engines.setdefault(app, {}) # Dispose existing engines in case init_app is called again. if engines: for engine in engines.values(): engine.dispose() engines.clear() # Create the metadata and engine for each bind key. for key, options in engine_options.items(): self._make_metadata(key) options.setdefault("echo", echo) options.setdefault("echo_pool", echo) self._apply_driver_defaults(options, app) engines[key] = self._make_engine(key, options, app) if app.config.setdefault("SQLALCHEMY_RECORD_QUERIES", False): from . import record_queries for engine in engines.values(): record_queries._listen(engine) if app.config.setdefault("SQLALCHEMY_TRACK_MODIFICATIONS", False): from . import track_modifications track_modifications._listen(self.session) 39
40. Plugins reaching EOL 40
41. See pallets-eco 41
42. That's all folks 42