app.py

from flask import Flask
from flask_restful import Resource, Api, reqparse, abort, fields, marshal_with
from flask_sqlalchemy import SQLAlchemy


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

class ToDoModel(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    task=db.Column(db.String(200))
    summary=db.Column(db.String(500))



task_post_args=reqparse.RequestParser()
task_post_args.add_argument('task', type=str, help='Task is required' , required=True)
task_post_args.add_argument('summary', type=str, help='Summary is required' , required=True)

task_update_args = reqparse.RequestParser()
task_update_args.add_argument('task', type=str)
task_update_args.add_argument('summary', type=str)

resource_fields={
    'id': fields.Integer,
    'task': fields.String,
    'summary': fields.String,

}

class ToDoList(Resource):
    def get(self):
        tasks=ToDoModel.query.all()
        todos={}
        for task in tasks:
            todos[task.id] = {'task': task.task, 'summary':task.summary}
        return todos


class ToDo(Resource):
    @marshal_with(resource_fields)
    def get(self, todo_id):
        task=ToDoModel.query.filter_by(id=todo_id).first()
        if not task:
            abort(404, message='Could not find task with the given id.')
        return task

    @marshal_with(resource_fields)
    def post(self, todo_id):
        args=task_post_args.parse_args()
        task=ToDoModel.query.filter_by(id=todo_id).first()
        if task:
            abort(409, message='task id is taken')

        todo=ToDoModel(id=todo_id, task=args['task'], summary=args['summary'])
        db.session.add(todo)
        db.session.commit()
        return todo, 201

    @marshal_with(resource_fields)
    def put(self, todo_id):
        args=task_update_args.parse_args()
        task = ToDoModel.query.filter_by(id=todo_id).first()
        if not task:
            abort(404, message="task doesnot exist, cannot update")
        if args['task']:
            task.task=args['task']
        if args['summary']:
            task.summary=args['summary']
        db.session.commit()
        return task

    def delete(self, todo_id):
        task = ToDoModel.query.filter_by(id=todo_id).first()
        db.session.delete(task)
        return 'ToDo deleted', 204


api.add_resource(ToDo,'/todos/<int:todo_id>')
api.add_resource(ToDoList, '/todos')

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