Improved structure

- Flask app factory instead of initializing `app` variable
- Gunicorn for production server
- Makefile: python3 -m
- .gitignore: instance dir

.gitignore

@@ -2,6 +2,7 @@ __pycache__/
 .mypy_cache/
 
 venv/
+instance/
 
 .vscode/
 .idea/

Makefile

@@ -1,8 +1,8 @@
 dev:
-	FLASK_DEBUG="true" flask run
+	FLASK_DEBUG="true" python3 -m flask run
 
 prod:
-	flask run
+	python3 -m gunicorn -w 4 "app:create_app()"
 
 format:
 	python3 -m autopep8 -r --in-place flaskapp/

app.py

@@ -1 +1 @@
-from flaskapp.app import app
+from flaskapp.app import create_app

flaskapp/__init__.py

@@ -1,3 +0,0 @@
-"""Init file for the module"""
-
-from .app import app

flaskapp/app.py

@@ -1,20 +1,33 @@
-"""Flask web application
-main script"""
+"""Flask web application main script"""
 
+import os
+import secrets
 from pathlib import Path
 
 from flask import Flask
 
 
+def create_app() -> Flask:
+    """Flask app factory function"""
+
     root = Path('..')
     static = str(root / 'static')
     tmpl = str(root / 'templates')
 
     app = Flask(
-    '${REPO_NAME_SNAKE}',
+        __name__,
         static_folder=static,
         template_folder=tmpl,
+        instance_relative_config=True,
+    )
+    app.config['SECRET_KEY'] = os.getenv(
+        'SECRET_KEY',
+        secrets.token_hex(32),
     )
 
-if __name__ == '__main__':
-    app.run()
+    try:
+        os.makedirs(app.instance_path)
+    except OSError:
+        pass
+
+    return app

requirements.txt

@@ -1 +1,2 @@
 flask==2.2.2
+gunicorn==20.1.0