{
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  {
   "cell_type": "markdown",
   "id": "476288d6",
   "metadata": {},
   "source": [
    "# Task 2: Mask Code\n",
    "\n",
    "You are given a list of codes in many random format.\n",
    "\n",
    "Write a script to mask first four characters (a-z,0-9) and keep the rest as it is.\n",
    "Example 1\n",
    "```\n",
    "Input: @list = ('ab-cde-123', '123.abc.420', '3abc-0010.xy')\n",
    "Output: ('xx-xxe-123', 'xxx.xbc.420', 'xxxx-0010.xy')\n",
    "```\n",
    "Example 2\n",
    "```\n",
    "Input: @list = ('1234567.a', 'a-1234-bc', 'a.b.c.d.e.f')\n",
    "Output: ('xxxx567.a', 'x-xxx4-bc', 'x.x.x.x.e.f')\n",
    "````"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "2226efbf",
   "metadata": {},
   "outputs": [],
   "source": [
    "import re"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "id": "ba2106d7",
   "metadata": {},
   "outputs": [],
   "source": [
    "ex1 = ('ab-cde-123', '123.abc.420', '3abc-0010.xy')\n",
    "ex2 = ('1234567.a', 'a-1234-bc', 'a.b.c.d.e.f')"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "65f5f1bb",
   "metadata": {},
   "source": [
    "First step is to mask a single code using pythons re.sub(). re.sub has a named argument ```count=4``` which will substitute the required number of matches.  \\w regex matches alphanumeric characters."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "id": "56d192cb",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'xx-xxe-123'"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "re.sub(r'[\\w]', 'x', ex1[0], count=4)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "8834b502",
   "metadata": {},
   "source": [
    "Next wrap this in a function which handles a list of codes to mask.  Using map() with a lambda function as the first argument is a common idiom in python."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "id": "54223d5f",
   "metadata": {},
   "outputs": [],
   "source": [
    "def mask_list_of_codes(loc):\n",
    "    result = map(lambda code: re.sub(r'[\\w]', 'x', code, count=4), loc)\n",
    "    return list(result)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "a9daffb3",
   "metadata": {},
   "source": [
    "Finally test the function with the examples above:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "id": "3aea4dac",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['xx-xxe-123', 'xxx.xbc.420', 'xxxx-0010.xy']"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "mask_list_of_codes(ex1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "id": "30d532a7",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['xxxx567.a', 'x-xxx4-bc', 'x.x.x.x.e.f']"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "mask_list_of_codes(ex2)"
   ]
  }
 ],
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