Construct a sqlite-specific variant Insert construct. The sqlalchemy.dialects.sqlite.insert() function creates a sqlalchemy.dialects.sqlite.Insert. The Insert construct includes additional methods Insert.on_conflict_do_update(), Insert.on_conflict_do_nothing().
from sqlalchemy.dialects.sqlite import insert
session.execute(insert(Date).values(
[{"date": date_} for date_ in new_dates]).on_conflict_do_nothing())