Pets Back End Update Route

Learning objective: By the end of this lesson, students will be able to create a new route to update a single pet by interacting with the database and sending a JSON response to the client.

UPDATE - Update route

In this section, we will create a new route to update a single pet. This route will be a PUT request to /pets/<pet_id>, and will return a JSON response with the updated pet.

We will be following these specs when building the route:

• CRUD Action: UPDATE
• Method: PUT
• Path: /pets/<pet_id>
• Response: JSON
• Success Status Code: 202
• Success Response Body: A JSON object with the updated pet.

• Error Status Code: 500

  404

• Error Response Body: A JSON object with a error message describing the error.

Let’s get started! 🎉

Defining the route

Let’s create a new route to update a single pet.

The method for this route is PUT, and the path is /pets/<pet_id>. Use the @app.route() decorator with the url path and the methods option to create the route.

Add the following to app.py:

## app.py
@app.route('/pets/<pet_id>', methods=['PUT'])
def update_pet(pet_id):
    return f"Updating the pet with the id {pet_id}"

Before moving on, we should test this route to ensure it works.

Open Postman and send a PUT request to http://localhost:5000/pets/1. You should receive a JSON response with the Updating the pet with the id 1 message.

Updating a single pet in SQL

We have tested the route, so let’s query the database and update a single pet. We can use an UPDATE pets SQL query including the pet_id for the WHERE clause and the values in request.json for the values to SET.

@app.route('/pets/<pet_id>', methods=['PUT'])
def update_pet(pet_id):
    try:
      connection = get_db_connection()
      cursor = connection.cursor(cursor_factory=psycopg2.extras.RealDictCursor)
      cursor.execute("UPDATE pets SET name = %s, age = %s, breed = %s WHERE id = %s RETURNING *", (request.json['name'], request.json['age'], request.json['breed'], pet_id))
      updated_pet = cursor.fetchone()
      if updated_pet is None:
        return "Pet Not Found", 404
      connection.commit()
      connection.close()
      return updated_pet, 202
    except Exception as e:
      return str(e), 500

Open up Postman and set up a PUT request to /pets/<pet_id>, including a JSON body with all the properties of a pet object: name, age, and breed.

You should receive the successfully updated object as a response.

💡 If you try to update a a pet that doesn’t exist or has been deleted, you should receive a 404 response. However, sending a request that doesn’t contain all the fields we listed in our UPDATE statement, will produce a 500 error with the name of the missing properties.