GCJ 2008 Qualification

a.py

#!/usr/bin/env python

from sys import stdin
from sets import Set

for case in xrange(int(stdin.readline())):
    num_engines = int(stdin.readline())
    engines = []
    for _ in xrange(num_engines):
        engines.append(stdin.readline())
    seq_set = Set([])
    min_switches = 0
    for _ in xrange(int(stdin.readline())):
        query = stdin.readline()
        seq_set.add(query)
        if len(seq_set) == num_engines:
            seq_set = Set([query])
            min_switches += 1
    print 'Case #%i: %i' % (case + 1, min_switches)

sets exist in the main namespace

seq_set = set() # no empty list required. it's the same if omitted.