01_07.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# NLP Basics: Learning how to use regular expressions"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Using regular expressions in Python\n",
    "\n",
    "Python's `re` package is the most commonly used regex resource. More details can be found [here](https://docs.python.org/3/library/re.html)."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "import re\n",
    "\n",
    "re_test = 'This is a made up string to test 2 different regex methods'\n",
    "re_test_messy = 'This      is a made up     string to test 2    different regex methods'\n",
    "re_test_messy1 = 'This-is-a-made/up.string*to>>>>test----2\"\"\"\"\"\"different~regex-methods'"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Splitting a sentence into a list of words"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['This',\n",
       " 'is',\n",
       " 'a',\n",
       " 'made',\n",
       " 'up',\n",
       " 'string',\n",
       " 'to',\n",
       " 'test',\n",
       " '2',\n",
       " 'different',\n",
       " 'regex',\n",
       " 'methods']"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "re.split('\\s', re_test)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['This',\n",
       " '',\n",
       " '',\n",
       " '',\n",
       " '',\n",
       " '',\n",
       " 'is',\n",
       " 'a',\n",
       " 'made',\n",
       " 'up',\n",
       " '',\n",
       " '',\n",
       " '',\n",
       " '',\n",
       " 'string',\n",
       " 'to',\n",
       " 'test',\n",
       " '2',\n",
       " '',\n",
       " '',\n",
       " '',\n",
       " 'different',\n",
       " 'regex',\n",
       " 'methods']"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "re.split('\\s', re_test_messy)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['This',\n",
       " 'is',\n",
       " 'a',\n",
       " 'made',\n",
       " 'up',\n",
       " 'string',\n",
       " 'to',\n",
       " 'test',\n",
       " '2',\n",
       " 'different',\n",
       " 'regex',\n",
       " 'methods']"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "re.split('\\s+', re_test_messy)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['This-is-a-made/up.string*to>>>>test----2\"\"\"\"\"\"different~regex-methods']"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "re.split('\\s+', re_test_messy1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['This',\n",
       " 'is',\n",
       " 'a',\n",
       " 'made',\n",
       " 'up',\n",
       " 'string',\n",
       " 'to',\n",
       " 'test',\n",
       " '2',\n",
       " 'different',\n",
       " 'regex',\n",
       " 'methods']"
      ]
     },
     "execution_count": 7,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "re.split('\\W+', re_test_messy1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['This',\n",
       " 'is',\n",
       " 'a',\n",
       " 'made',\n",
       " 'up',\n",
       " 'string',\n",
       " 'to',\n",
       " 'test',\n",
       " '2',\n",
       " 'different',\n",
       " 'regex',\n",
       " 'methods']"
      ]
     },
     "execution_count": 10,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "re.findall('\\S+', re_test)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['This',\n",
       " 'is',\n",
       " 'a',\n",
       " 'made',\n",
       " 'up',\n",
       " 'string',\n",
       " 'to',\n",
       " 'test',\n",
       " '2',\n",
       " 'different',\n",
       " 'regex',\n",
       " 'methods']"
      ]
     },
     "execution_count": 11,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "re.findall('\\S+', re_test_messy)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['This-is-a-made/up.string*to>>>>test----2\"\"\"\"\"\"different~regex-methods']"
      ]
     },
     "execution_count": 12,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "re.findall('\\S+', re_test_messy1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['This',\n",
       " 'is',\n",
       " 'a',\n",
       " 'made',\n",
       " 'up',\n",
       " 'string',\n",
       " 'to',\n",
       " 'test',\n",
       " '2',\n",
       " 'different',\n",
       " 'regex',\n",
       " 'methods']"
      ]
     },
     "execution_count": 13,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "re.findall('\\w+', re_test_messy1)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Replacing a specific string"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "pep8_test = 'I try to follow PEP8 guidelines'\n",
    "pep7_test = 'I try to follow PEP7 guidelines'\n",
    "peep8_test = 'I try to follow PEEP8 guidelines'"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "collapsed": true
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['try', 'to', 'follow', 'guidelines']"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "import re\n",
    "re.findall(\"[a-z]+\", pep8_test)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['I', 'PEP']"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "re.findall(\"[A-Z]+\", pep8_test)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['I', 'PEP8']"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "re.findall(\"[A-Z0-9]+\", pep8_test)# capture letters or numbers "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['PEP8']"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "re.findall(\"[A-Z]+[0-9]+\", pep8_test) # capture letters and numbers "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'I try to follow PEP8 Python Styleguide guidelines'"
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "re.sub(\"[A-Z]+[0-9]+\", \"PEP8 Python Styleguide\", pep8_test)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'I try to follow PEP8 Python Styleguide guidelines'"
      ]
     },
     "execution_count": 9,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "re.sub(\"[A-Z]+[0-9]+\", \"PEP8 Python Styleguide\", pep7_test)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'I try to follow PEP8 Python Styleguide guidelines'"
      ]
     },
     "execution_count": 10,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "re.sub(\"[A-Z]+[0-9]+\", \"PEP8 Python Styleguide\", peep8_test)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "collapsed": true
   },
   "source": [
    "### Other examples of regex methods\n",
    "\n",
    "- re.search()\n",
    "- re.match()\n",
    "- re.fullmatch()\n",
    "- re.finditer()\n",
    "- re.escape()"
   ]
  }
 ],
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