init

.gitignore

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+/venv
+/__pycache__

app.py

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+from flask import Flask, g
+import sqlite3
+
+app = Flask(__name__)
+
+def connect_db():
+    sql = sqlite3.connect('./database.db')
+    sql.row_factory = sqlite3.Row
+    return sql
+
+
+def get_db():
+    #Check if DB is there
+    if not hasattr(g, 'sqlite3'):
+        g.sqlite3_db = connect_db()
+    return g.sqlite3_db
+
+#close the connection to the database automatically
+@app.teardown_appcontext
+def close_db(error):
+    #if global object has a sqlite database then close it. If u leave it open noone can access it and gets lost in memory causing leaks.
+    if hasattr(g, 'sqlite_db'):
+        g.sqlite3_db.close()
+
+@app.route('/')
+def index():
+    return f'<h1>Hello, World!</h1>'
+
+@app.route('/users')
+def viewusers():
+    db = get_db()
+    cursor = db.execute('select id, name, age from people')
+    results = cursor.fetchall()
+    return f"<h1>The Id is {results[0]['id']}.<br> The Name is {results[0]['name']}. <br> The age is {results[0]['age']}. </h1>"
+
+
+if __name__ == '__main__':
+    app.run(debug = True)

db.py

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+import sqlite3
+
+import click
+from flask import current_app
+from flask import g
+from flask.cli import with_appcontext
+
+
+def get_db():
+    """Connect to the application's configured database. The connection
+    is unique for each request and will be reused if this is called
+    again.
+    """
+    if "db" not in g:
+        g.db = sqlite3.connect(
+            current_app.config["DATABASE"], detect_types=sqlite3.PARSE_DECLTYPES
+        )
+        g.db.row_factory = sqlite3.Row
+
+    return g.db
+
+
+def close_db(e=None):
+    """If this request connected to the database, close the
+    connection.
+    """
+    db = g.pop("db", None)
+
+    if db is not None:
+        db.close()
+
+
+def init_db():
+    """Clear existing data and create new tables."""
+    db = get_db()
+
+    with current_app.open_resource("schema.sql") as f:
+        db.executescript(f.read().decode("utf8"))
+
+
+@click.command("init-db")
+@with_appcontext
+def init_db_command():
+    """Clear existing data and create new tables."""
+    init_db()
+    click.echo("Initialized the database.")
+
+
+def init_app(app):
+    """Register database functions with the Flask app. This is called by
+    the application factory.
+    """
+    app.teardown_appcontext(close_db)
+    app.cli.add_command(init_db_command)

requirements.txt

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+click==8.0.3
+Flask==2.0.2
+itsdangerous==2.0.1
+Jinja2==3.0.2
+MarkupSafe==2.0.1
+Werkzeug==2.0.2

schema.sql

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+-- Initialize the database.
+-- Drop any existing data and create empty tables.
+
+DROP TABLE IF EXISTS user;
+
+CREATE TABLE user (
+  id INTEGER PRIMARY KEY AUTOINCREMENT,
+  name TEXT NOT NULL,
+  age TEXT NOT NULL
+);