Project Euler Q35 - LO Man Hei

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    "### Q35\n",
    "How many circular primes are there below one million?"
   ]
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    "def prime_numbers(n, max_len = False):\n",
    "    result = []\n",
    "    if max_len:\n",
    "        n = max_len**2//5000 + max_len*20\n",
    "    sieve = [True] * (n+1)\n",
    "    for p in range(2, n+1):\n",
    "        if (sieve[p]):\n",
    "            result.append(p)\n",
    "            if max_len and len(result) >= max_len:\n",
    "                return result\n",
    "            for i in range(p, n+1, p):\n",
    "                sieve[i] = False\n",
    "    return result\n",
    "\n",
    "def circular_primes_under_n(n):\n",
    "    primes_list = set(prime_numbers(n))\n",
    "    drop_prime = set()\n",
    "    for p in primes_list:\n",
    "        str_p = str(p)\n",
    "        if len(str_p) >=2 and any(str(i) in str_p for i in [2,4,5,6,8,0]):\n",
    "            drop_prime.add(p)\n",
    "    for p in primes_list:\n",
    "        if p in drop_prime:\n",
    "            continue\n",
    "        str_p = str(p)\n",
    "        if int(str_p[1:]+str_p[:1]) not in primes_list :\n",
    "            for i in range(0,len(str_p)):\n",
    "                drop_prime.add(int(str_p[i:]+str_p[:i]))\n",
    "    return primes_list.difference(drop_prime)"
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      "CPU times: user 169 ms, sys: 0 ns, total: 169 ms\n",
      "Wall time: 166 ms\n"
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   "source": [
    "%%time\n",
    "len(circular_primes_under_n(1000000))"
   ]
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