I could not find any nice examples of using the vobject class to filter an icalendar file. Here is what I got to work. I'm sure there is a nicer way. This strips all of the valarm subevents (reminders) from an icalendar file.

import vobject
import sys

cal=vobject.readOne(sys.stdin)

for ev in cal.vevent_list:
    if ev.contents.has_key(u'valarm'):
       del ev.contents[u'valarm']

print cal.serialize()