Question

I have a model of the form:

class MyModel(base):
    # ...
    datetime = Column(DateTime)
    # ...

and would like to create a .date and a .time property which correspond to the .datetime column. The SQLA documentations shows a couple of examples of combining properties (such as firstname + lastname => fullname) but nothing for decomposing.

I think using @hybrid_property and friends I can do the initial decomposition but am unsure about assignment (so if n = MyModel.query...one() I wish to be able to do n.date = d and have it update the .datetime field.)

My primary RDBMS is MySQL.

(For those that are interested in my motivation for wanting to do this: I have a lot of client-side code which is duck-typed to expect .date and .time fields however many stored procedures and triggers on the server expect a single .datetime column.)

Answer 1

The docs say explicitly that you can do this, you need to use the @hybrid.property and @value.setter decorators and your own code to return the date or time in the expected format:

from sqlalchemy.ext.hybrid import hybrid_property

class SomeClass(object):
    @hybrid_property
    def value(self):
        return self._value

    @value.setter
    def value(self, value):
        self._value = value

Full disclosure: I have used the property feature but not the setter feature.