Not being able to POST negative numbers by Postman, how to do that?

December 9, 2021

I have a Python app that uses Postman to GET and POST data’s to/from MongoDB. It is a simple GasStation app, but it let’s us POST negative numbers. How to validate that doesn’t allow negative numbers?

@server_api.route('/add_data', methods=['POST'])
def receive_data():
    data_received = request.get_json()
    if "PetrolCapacity" not in data_received or "DieselCapacity" not in data_received:
        return Response("Bad arguments", 400)
    print(data_received)
    service.push_to_database(data_received)
    return Response("Data received successfully", 200)


@server_api.route('/get_data', methods=['GET'])
def return_data():
    last_element = service.query_last_element()
    print(last_element)

    data = last_element['PetrolCapacity']
    return data

>Solution :

You can just compare them like this:

@server_api.route('/add_data', methods=['POST'])
def receive_data():
    data_received = request.get_json()
    if "PetrolCapacity" not in data_received or "DieselCapacity" not in data_received:
        return Response("Bad arguments", 400)

    petrol_capacity = data_received["PetrolCapacity"]
    for tank in petrol_capacity:
        if petrol_capacity[tank] < 0:
            return Response("Negative values not allowed", 400)

    if data_received["DieselCapacity"] < 0:
        return Response("Negative values not allowed", 400)

    print(data_received)
    service.push_to_database(data_received)
    return Response("Data received successfully", 200)


@server_api.route('/get_data', methods=['GET'])
def return_data():
    last_element = service.query_last_element()
    print(last_element)

    data = last_element['PetrolCapacity']
    return data