ProjectEuler#35 Circular primes

#The number, 197, is called a circular prime because all rotations of the
#digits: 197, 971, and 719, are themselves prime.

#There are thirteen such primes below 100:
#2, 3, 5, 7, 11, 13, 17, 31, 37, 71, 73, 79, and 97.

#How many circular primes are there below one million?

def isPrime(n):
    '''check if integer n is a prime'''
    # range starts with 2 and only needs to go up the square-root of n
    for x in range(2, int(n**0.5)+1):
        if n % x == 0:
            return False
    return True

def isCirPrime(n):
    '''check if integer n is a circular prime'''
    if n < 10:
        return True
    nstr = str(n)
    for i in range(len(nstr)-1):
        nstr = nstr[1:]+nstr[0]
        if not isPrime(int(nstr)):
            return False
    return True

cirPrimes = [2]

for i in range(3,1000000,2): #Checks only odd numbers for prime
    if isPrime(i) and isCirPrime(i):
        cirPrimes.append(i)

print len(cirPrimes)