Right way to update a date attribute in a database? - postgresql

Question

I am looking for a way to update data input (date format) inside a database.
Client app --> Flask --> Database
I am unsure about the best way for processing that needs to be done within Flask.
Data from the client app comes in JSON and may look like this:
data = [{"id": 1, "date": "2022-01-01"}, {"id": 2, "date": null}]
Note that date can also be null.
Currently I am processing the date input in the following way. Is there a better way to do this instead of manually checking if the provided data is empty?
import datetime
#app.route('/update_date', methods=['POST'])
def update_date():
data = request.json['data']
for item in data:
# query db object
example = db.session.query(Example).filter_by(id=data['id']).first()
# checking if input exists --> looking for a better way to do this
if item['date'] == '' or item['date'] is None:
example.date = None
else:
# convert string date to actual date object
example.date = datetime.datetime.strptime(data['date'], '%d.%m.%Y')
db.session.commit()
One drawback of this method is that the data input needs to be in the format specified in the strptime function. If the data comes in a different format it will raise an error. But there has to be a better way than to just add anotehr elif statement, right?
database model:
from flask_sqlalchemy import SQLAlchemy
from sqlalchemy import Date
db = SQLAlchemy()
class Example(db.Model):
id = db.Column(db.Integer, primary_key=True)
date = db.Column(db.Date)

Answer 1

As mentionned in my previous comment, you can validate and process the input coming from the front end.
An example using voluputous and defining a custom validator could look like :
from datetime import datetime
from voluptuous import Coerce, Date, Maybe, Schema
def Date(fmt):
return lambda v: datetime.strptime(v, fmt).date()
# Maybe : Validate that the object matches given validator or is None.
validate = Schema([{"id": int, "date": Maybe(Coerce(Date("%Y-%m-%d")))}])
with_date = [{"id": 1, "date": "2022-08-17"}]
without_date = [{"id": 2, "date": None}]
with_bad_date = [{"id": 2, "date": "2022-99-99"}]
validate(with_date) # [{'id': 1, 'date': datetime.date(2022, 8, 17)}]
validate(without_date) # [{'id': 1, 'date': None}]
validate(with_bad_date) # MultipleInvalid: not a valid value for dictionary value # data[0]['date']