{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# RE module"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "import re\n",
    "import numpy as np"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### 1. To extract a pattern in a given string - Use `re.findall(pattern, text)`\n",
    "\n",
    "Returns a list containing all matches.\n",
    "\n",
    "In the example below we try to extract string of three consecutive numbers."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['619', '999', '871']"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "text = 'Jeswin 619 George 999 98Y Y27J0 JK871'\n",
    "re.findall(r'\\d{3}', text)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Now to get the first or last patterns use indexing."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'619'"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "re.findall(r'\\d{3}', text)[0]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'871'"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "re.findall(r'\\d{3}', text)[-1]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### 2. To substitute a pattern with a string of your choice - `re.sub(pattern, desired_string, text)`\n",
    "\n",
    "replaces the matches with the text of your choice."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [],
   "source": [
    "text = 'Jeswin 619 George 999 98Y Y27J0 JK871'"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "To replace __Y__ with string __B__."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'Jeswin 619 George 999 98B B27J0 JK871'"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "re.sub('Y', \"B\", text)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "In the given text, ensure that the alpha-numeric words doesnt have alphabets and resulting numeric word must have only numerics and must have length of 3 (You can use any numeric of your choice)."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [],
   "source": [
    "output = []\n",
    "for word in text.split():\n",
    "    if re.findall(r'\\d', word):\n",
    "        if re.findall(r'[A-Z]',word):\n",
    "            word = re.sub(r'[A-Z]', '5', word)\n",
    "            if len(word)==3:\n",
    "                output.append(word)\n",
    "            elif len(word)<3:\n",
    "                while (3-len(word))<=0:\n",
    "                    word += str(np.random.randomint(9))\n",
    "                output.append(word)\n",
    "            elif len(word)>3:\n",
    "                word = word[:3-len(word)]\n",
    "                output.append(word)\n",
    "        else:\n",
    "            output.append(word)\n",
    "                \n",
    "    else:\n",
    "        output.append(word)\n",
    "\n",
    "\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['Jeswin', '619', 'George', '999', '985', '527', '558']"
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "output"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Combining the list of words to a single sentence using [string join()](https://www.geeksforgeeks.org/python-string-join-method/)."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'Jeswin 619 George 999 985 527 558'"
      ]
     },
     "execution_count": 9,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "' '.join(output)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'Jeswin 619 George 999 98Y Y27J0 JK871'"
      ]
     },
     "execution_count": 10,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "text"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Reference\n",
    "\n",
    "![](images/1.PNG)\n",
    "\n",
    "![](images/2.PNG)\n",
    "\n",
    "![](images/3.PNG)"
   ]
  }
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