Solution
@app.route('/', methods=['GET', 'POST'])
def hello_world():
if request.method == 'POST':
title = request.form["title"]
desc = request.form["desc"]
todo = Todo(title=title, desc=desc)
db.session.add(todo)
db.session.commit()
mytodo = Todo.query.all()
return render_template('index.html', mytodo=mytodo)