How to return Json from Flask-SQLAlchemy

June 28, 2022

I am not able to return a JSON string, although it is possible if I request just one entry.

This works

@app.route('/incomeexpense/<id>', methods=['GET'])
def handle_incomexpense(id):
    incomeexpense = IncomeExpenseModel.query.get_or_404(id)

    if request.method == 'GET':
            response = {
                    "orderdate": incomeexpense.orderdate,
                    "who": incomeexpense.who,
                    "location": incomeexpense.location,
                    "income": incomeexpense.income,
                    "expense": incomeexpense.expense
            }
            return {"message": "success", "incomeexpense": response}

This does not work

@app.route('/incomeexpense/all', methods=['GET'])
def handle_incomexpense_all():
    incomeexpense = IncomeExpenseModel.query.all();

    if request.method == 'GET':
            response = {
                    "orderdate": incomeexpense.orderdate,
                    "who": incomeexpense.who,
                    "location": incomeexpense.location,
                    "income": incomeexpense.income,
                    "expense": incomeexpense.expense
            }
            return {"message": "success", "incomeexpense": response}

Here is my model

class IncomeExpenseModel(db.Model):
    __tablename__ = 'incomeexpense'

    id = db.Column(db.Integer, primary_key=True)
    orderdate = db.Column(db.String())
    who = db.Column(db.String())
    location = db.Column(db.Integer())
    income = db.Column(db.Numeric(16,2), nullable=True)
    expense = db.Column(db.Numeric(16,2), nullable=True)

    def __init__(self, orderdate, who, location, income, expense):
            self.orderdate = orderdate
            self.who = who
            self.location = location
            self.income = income
            self.expense = expense

Maybe someone can tell me how to return a JSON string?

Thank you very much in advance.

>Solution :

incomeexpense = IncomeExpenseModel.query.all()
This line returns list of objects.

If you want to return JSON with one object you can use indexing, like:
incomeexpense = IncomeExpenseModel.query.all()[0]

Or If you want to return all of them, prepare response using loop:

responses = []
for incomeexpense in IncomeExpenseModel.query.all():
    responses.append({
        "orderdate": incomeepense.orderdate
        ...
    })