Project Euler Q58 - LO Man Hei

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    "### Q58\n",
    "If one complete new layer is wrapped around the spiral above, a square spiral with side length 9 will be formed. If this process is continued, what is the side length of the square spiral for which the ratio of primes along both diagonals first falls below 10%?"
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    "def is_prime(n):\n",
    "    for i in range(2,int(n**0.5)+1):\n",
    "        if (n%i) == 0:\n",
    "            return False\n",
    "    return True\n",
    "\n",
    "def spiral_primes_ratio_under_r(r):\n",
    "    n = 0\n",
    "    last_num = 1\n",
    "    num_count = 1\n",
    "    prime_count = 0\n",
    "    while n < 1 or prime_count / num_count > r:\n",
    "        n += 1\n",
    "        for o in range(4):\n",
    "            last_num += 2*n\n",
    "            num_count += 1\n",
    "            prime_count += 1 if is_prime(last_num) else 0\n",
    "    return n"
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      "Wall time: 3.13 s\n"
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    "%%time\n",
    "spiral_primes_ratio_under_r(0.1)"
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