ProjectEuler#41 Pandigital prime

#We shall say that an n-digit number is pandigital if it makes use of all
#the digits 1 to n exactly once. For example, 2143 is a 4-digit pandigital
#and is also prime.

#What is the largest n-digit pandigital prime that exists?

import itertools

def isPrime(n):
    '''check if integer n is a prime'''
    if n < 2:
        return False
    # 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 generatePerm(nDigits):
    #tupleList is sorted asc
    tupleList = list(itertools.permutations(range(1,nDigits+1),nDigits))
    intList = []
    for i in tupleList: #Convert tuples list generated to ints list
        digitStr = ''
        for j in i:
            digitStr += str(j)
        if int(digitStr)%2 != 0: #add to ints list only odd numbers
            intList.append(int(digitStr)) #(evens are not primes)
    return intList

largest = 0
for i in range(9,0,-1):
    intList = generatePerm(i)
    for j in range(len(intList)-1,-1,-1): #iterate backwards (list sorted asc)
        if isPrime(intList[j]):
            largest = intList[j]
            break
    if largest != 0:
        break
print largest


#Improvement - Not Implemented:
#only 4 or 7 digit numbers need to be considered.
#Proof: the sum of the digits is 1+2+3+...+n = n(n+1)/2. It is divisible by 3
#if n or n+1 are divisible by 3. So only n = 1, 4, 7 are such that n(n+1)/2 is
#not divisible by 3. 1 can be ignored since 1 is not prime.
#Source: Project Euler ernacktob solution.