Question

The result should be Date object

Since the day cannot be ‘removed’, set it to say, 1st day of the month.

Leaving only Month, Year

Answer 1

You can use following constructs to filter the Date column using either year or month:

.filter(extract('year', Foo.Date) == 2012)
.filter(extract('month', Foo.Date) == 12)

And group_by is also possible:

.group_by(sqlalchemy.func.year(Foo.Date), sqlalchemy.func.month(Foo.Date))

Now I haven’t tested it, but I assume that this might be slow because these queries result in full table scans, therefore I suggest you invest some time and learn how to use composite columns.

Note: extract() is imported from sqlalchemy.sql