Callbacks and Events

perspective.Table allows for on_update and on_delete callbacks to be set—simply call on_update or on_delete with a reference to a function or a lambda without any parameters:

def update_callback():
    print("Updated!")

# set the update callback
on_update_id = view.on_update(update_callback)


def delete_callback():
    print("Deleted!")

# set the delete callback
on_delete_id = view.on_delete(delete_callback)

# set a lambda as a callback
view.on_delete(lambda: print("Deleted x2!"))

If the callback is a named reference to a function, it can be removed with remove_update or remove_delete:

view.remove_update(on_update_id)
view.remove_delete(on_delete_id)

Callbacks defined with a lambda function cannot be removed, as lambda functions have no identifier.

on_remove fires when rows are removed from a View’s Table with an index, and receives the port ID and the removed index values as an Apache Arrow (bytes) of one column named after the index:

def remove_callback(port_id, indices):
    print("Removed", client.table(indices).view().to_records())

on_remove_id = view.on_remove(remove_callback)
view.remove_remove(on_remove_id)