Is there a database independent way to filter by "None"/"NaN"?

The following code is database specific:

im开发者_如何学Cport sqlalchemy
# ...
ergebnis = session.query(
    my_object.attr1).filter(sa.and_(
        my_object.attr2 != 'NaN')).all() # PostgreSQL
        """
        my_object.attr2 != None)).all() # sQLite
        """

With PostgreSQL it is "'NaN'", with SQLite "None" (without single quotes). Is there an SQLAlchemy way to do this backend independent?

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If you want to compare against the 'NaN' ("not a number") float value, then do an explicit cast to float: float('NaN'). In this case SQLAlchemy should do the same conversion.

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This seems to work for Postgres, but I don't know how database-independent it is:

import sqlalchemy as sqla

...

myobject.attr2 != sqla.cast(float("NaN"), sqla.Float)