bloom_filter.ipynb

{
 "cells": [
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "import hashlib"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [],
   "source": [
    "class BloomFilter:\n",
    "    \n",
    "    def __init__(self, num_bits, num_hashes):\n",
    "        self.num_bits = num_bits\n",
    "        self.num_hashes = num_hashes\n",
    "        self.bit_vec = [0] * num_bits\n",
    "        \n",
    "    def generate_hash_for_item(self, item, hash_id):\n",
    "        assert type(item) == str, \"Only supporting strings at the moment\"\n",
    "        m = hashlib.sha256()\n",
    "        m.update(bytes((item + str(hash_id)).encode('utf-8')))        \n",
    "        return int(m.hexdigest(), 16)        \n",
    "    \n",
    "    def add_item(self, item):\n",
    "        for hash_id in range(self.num_hashes):\n",
    "            bit_to_set = self.generate_hash_for_item(item, hash_id) % self.num_bits\n",
    "            self.bit_vec[bit_to_set] = 1\n",
    "            \n",
    "    def check_item(self, item):\n",
    "        assert type(item) == str, \"Only supporting strings at the moment\"\n",
    "        for hash_id in range(self.num_hashes):\n",
    "            bit_to_check = self.generate_hash_for_item(item, hash_id) % self.num_bits\n",
    "            if self.bit_vec[bit_to_check] == 0:\n",
    "                return False\n",
    "        return True\n",
    "        \n",
    "        \n",
    "            \n",
    "        "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "True\n",
      "False\n"
     ]
    }
   ],
   "source": [
    "b = BloomFilter(128, 10)\n",
    "b.add_item(\"hello\")\n",
    "print(b.check_item(\"hello\"))\n",
    "print(b.check_item(\"world\"))"
   ]
  }
 ],
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