app.py

from flask import Flask,render_template,url_for,request,redirect
from flask_sqlalchemy import SQLAlchemy
from datetime import datetime 

app=Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI']='sqlite:///test.db'
db=SQLAlchemy(app)

class Todo(db.Model):
    id=db.Column(db.Integer,primary_key=True)
    content = db.Column(db.String(200),nullable=False)
    date_created = db.Column(db.DateTime,default=datetime.utcnow)

    def __repr__(self):
        return '<task %r>' % self.id

@app.route('/',methods=['POST','GET'])
def index():
    if request.method=="POST":
        task_content=request.form['content']
        new_task=Todo(content=task_content)

        try:
            db.session.add(new_task)
            db.session.commit()
            return redirect('/')

        except:
            return'Error adding the new task' 
    else:
        tasks= Todo.query.order_by(Todo.date_created).all()
        return render_template('index.html',tasks=tasks)

@app.route('/delete/<int:id>')
def delete(id):
    task_to_delete=Todo.query.get_or_404(id)
    try:
        db.session.delete(task_to_delete)
        db.session.commit()
        return redirect('/')
    except:
        return 'Error deleting the new task' 

@app.route('/update/<int:id>',methods=['POST','GET'])
def update(id):
    task=Todo.query.get_or_404(id)
    if request.method=="POST":
        task.content=request.form['content']
        try:
            db.session.commit()
            return redirect('/')
        except:
            return 'Error updating the task'
    else:
        return render_template('update.html',task=task)


if __name__ == "__main__":
    app.run(debug=True)