Euler 35 - python solution taking too long
Your p is a list.  Then you do p.count(x) to see if x is a prime.  This does a linear search of the list, and in fact, has to examine every element of p, not just those up to the occurrence of x.  Instead, change p to a set.  It will run much faster.  Also, once you see that a rotation is not prime, you can stop checking all the rotations.