todo.py

from flask import Flask,render_template,redirect,url_for,request
from flask_sqlalchemy import SQLAlchemy
app=Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////Users/LENOVO/Desktop/TodoApp/todo.db'
db=SQLAlchemy(app)
@app.route("/")
def index():
    todos=Todo.query.all()
    return render_template("index.html",todos=todos)
@app.route("/add",methods=["POST"])
def add():
    title=request.form.get("title")
    newTodo=Todo(title=title,complete=False)
    db.session.add(newTodo)
    db.session.commit()
    return redirect(url_for("index"))
@app.route("/complete/<string:id>")
def completeTodo(id):
    todo=Todo.query.filter_by(id=id).first()
    todo.complete = not todo.complete
    db.session.commit()
    return redirect(url_for("index"))
@app.route("/delete/<string:id>")
def deleteTodo(id):
    todo=Todo.query.filter_by(id=id).first()
    db.session.delete(todo)
    db.session.commit()
    return redirect(url_for("index"))
class Todo(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    title=db.Column(db.String(80))
    complete=db.Column(db.Boolean)
with app.app_context():
    db.create_all()    
if __name__=="__main__":
    app.run(debug=True)