problem with updating puppetclasses for a host

[svenXY]

Hi,
I'm trying to add a puppetclass to the puppetclasses of a host, but can't seem to find out how.

First attempt was something like:

pc = f.show_puppetclasses(p_id)
host = f.show_hosts(id)
host['puppetclasses'].append(pc)
f.update_hosts(id=host['id'], host=host)

but that does nothing and even returns an empty resultset

then

ppn = { 'puppetclass_id': 4212 }
f.update_hosts(id=host['id'], host=ppn)

this takes much longer and returns the host resultset, but the class is not added.

Maybe you have a hint?

Thanks,
Sven