Project Euler 35 (Broken)

#!/usr/bin/env python

# http://projecteuler.net/index.php?section=problems&id=48

import time, math, sieve
start = time.time()

def rotations(n):
    '''Returns all rotated values for n, as a set'''
    results = set()
    string = str(n)
    for i in range(len(string)):
        string = string[1:] + string[0]
        results.add(int(string))

    return results

# Get primes
primes = set(sieve.primeSieve(1000000))
results = set()

# For each prime:
while len(primes):
    # check primes for all the rotations
    p = primes.pop()
    primes.add(p)
    rots = rotations(p)
    print 'Rotations: ' + `rots`

    if rots.issubset(primes):
        # if they're all present, put them in results
        results = results.union(rots)
    # remove all the rotations from primes
    for r in rots:
        primes.discard(r)

total = len(results)

end = time.time()
print 'The total is ' + `total`
print 'This took ' + `end-start` + ' seconds to calculate.'