Count number of rows in a many-to-many relationship (SQLAlchemy)

Question

I have a many-to-many relationship between say blog entries and tags. Now I want to know how many entries a specific tag has.

Imagine the following models (simplifie

Answer 1

session.query(Entry).join(Entry.tags).filter(Tag.id==1).count()

or if you have a Tag already

session.query(Entry).with_parent(mytag, "entries").count()