app.py

from flask import Flask, request, jsonify
from flask_sqlalchemy import SQLAlchemy 
from flask_marshmallow import Marshmallow
import os

# Init app
app = Flask(__name__)
basedir= os.path.abspath(os.path.dirname(__file__))

#Database
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///' + os.path.join(basedir,'db.sqlite')
app.config['SQLALCHEMY_TRACK_MODIFICATION'] = True

#Init db
db=SQLAlchemy(app)

#Init ma
ma=Marshmallow(app)

# Product Class/Model
class Product(db.Model):
    id=db.Column(db.Integer,primary_key=True)
    name=db.Column(db.String(100),unique=True)
    description=db.Column(db.String(200))
    price=db.Column(db.Float)
    qty=db.Column(db.Integer)

    def __init__(self,name,description,price,qty):
        self.name=name
        self.description=description
        self.price=price
        self.qty=qty

# Product Schema 
class ProductSchema(ma.Schema):
    class Meta:
        fields=('id','name','description','price','qty')

#Init schema
product_schema=ProductSchema()
products_schema = ProductSchema(many=True)

# Create a Product
@app.route('/product',methods=['POST'])
def add_product():
    name=request.json['name']
    description=request.json['description']
    price=request.json['price']
    qty=request.json['qty']

    new_product=Product(name,description,price,qty)

    db.session.add(new_product)
    db.session.commit()

    return product_schema.jsonify(new_product)

# Get All Products
@app.route('/product',methods=['GET'])
def get_products():
    all_products=Product.query.all()
    result=products_schema.dump(all_products)
    return jsonify(result)

# Get Single Product
@app.route('/product/<id>',methods=['GET'])
def get_product(id):
    product=Product.query.get(id)
    return product_schema.jsonify(product)

# Update a Product
@app.route('/product/<id>',methods=['PUT'])
def update_product(id):
    product=Product.query.get(id)

    name=request.json['name']
    description=request.json['description']
    price=request.json['price']
    qty=request.json['qty']

    product.name=name
    product.description=description
    product.price=price
    product.qty=qty

    db.session.commit()

    return product_schema.jsonify(product)

# Delete Product
@app.route('/product/<id>',methods=['DELETE'])
def delete_product(id):
    product=Product.query.get(id)
    db.session.delete(product)
    db.session.commit()
    return product_schema.jsonify(product)

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