SQLAlchemy How to load dates with timezone=UTC (dates stored without timezone)

Question

I have a model with a date column defined as :

created_on = db.Column(db.DateTime, default=db.func.now(), nullable=False)

The dates comme out with tz_info=None, which is correct, since the dates are stored without timezone info.

If I print the date :

print(my_object.created_on.isoformat())

I get this format

2014-04-26T17:46:27.353936

I would like to have a UTC timezone indicator, such as :

2014-04-26T17:46:27.353936Z

Is there a way to define this behavior in the schema config ?

SQLAlchemy has, timezone=Boolean

sqlalchemy.types.DateTime(timezone=False)

since I want the storage to be without timezone.

Answer 1

You want a custom data type, described here: http://docs.sqlalchemy.org/en/rel_0_9/core/types.html#custom-types

Specifically, something like this:

import pytz  # from PyPI

class AwareDateTime(db.TypeDecorator):
    '''Results returned as aware datetimes, not naive ones.
    '''

    impl = db.DateTime

    def process_result_value(self, value, dialect):
        return value.replace(tzinfo=pytz.utc)

Then just make the column like this:

created_on = db.Column(AwareDateTime, default=db.func.now(), nullable=False)

Answer 2

I would recommend to use Arrow type.

from datetime import datetime
from sqlalchemy_utils import ArrowType
import arrow


class Article(Base):
    __tablename__ = 'article'
    id = sa.Column(sa.Integer, primary_key=True)
    name = sa.Column(sa.Unicode(255))
    created_at = sa.Column(ArrowType)



article = Article(created_at=arrow.utcnow())