The following code doesn't work, but a by hand tailored equivalent `random.choice(None or [None])` works just fine.

random_rows.py

def random_rows(db, model, columns={}, num=100):
    column_types = [ {'name': col.name, 'type': str(col.type)} for col in model.__table__.columns]
    rows = []
    for n in range(1, num):
        rows.append([random.choice(columns.get(col['name']) or [None]) or __random_data(col['type']) for col in column_types])
    return rows