1 - Keywords and Identifiers.ipynb

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   "source": [
    "# Python Keywords"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Keywords are the reserved words in python\n",
    "\n",
    "We can't use a keyword as variable name, function name or any other identifier\n",
    "\n",
    "Keywords are case sentive"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
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     "text": [
      "['and', 'as', 'assert', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'exec', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'not', 'or', 'pass', 'print', 'raise', 'return', 'try', 'while', 'with', 'yield']\n",
      "('Total number of keywords ', 31)\n"
     ]
    }
   ],
   "source": [
    "#Get all keywords in python 3.6\n",
    "\n",
    "import keyword\n",
    "\n",
    "print(keyword.kwlist)\n",
    "\n",
    "print(\"Total number of keywords \", len(keyword.kwlist))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "collapsed": true
   },
   "source": [
    "# Identifiers"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Identifier is the name given to entities like class, functions, variables etc. in Python. It helps differentiating one entity from another."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Rules for Writing Identifiers:\n",
    "\n",
    "1. Identifiers can be a combination of letters in lowercase (a to z) or uppercase (A to Z) or digits (0 to 9) or an underscore (_).\n",
    "\n",
    "2. An identifier cannot start with a digit. 1variable is invalid, but variable1 is perfectly fine.\n",
    "\n",
    "3. Keywords cannot be used as identifiers."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "ename": "SyntaxError",
     "evalue": "invalid syntax (<ipython-input-3-d0026cf49b71>, line 1)",
     "output_type": "error",
     "traceback": [
      "\u001b[0;36m  File \u001b[0;32m\"<ipython-input-3-d0026cf49b71>\"\u001b[0;36m, line \u001b[0;32m1\u001b[0m\n\u001b[0;31m    global = 1\u001b[0m\n\u001b[0m           ^\u001b[0m\n\u001b[0;31mSyntaxError\u001b[0m\u001b[0;31m:\u001b[0m invalid syntax\n"
     ]
    }
   ],
   "source": [
    "global = 1"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    " We cannot use special symbols like !, @, #, $, % etc. in our identifier."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "ename": "SyntaxError",
     "evalue": "invalid syntax (<ipython-input-5-b512271f00c8>, line 1)",
     "output_type": "error",
     "traceback": [
      "\u001b[0;36m  File \u001b[0;32m\"<ipython-input-5-b512271f00c8>\"\u001b[0;36m, line \u001b[0;32m1\u001b[0m\n\u001b[0;31m    a@ = 10             #can't use special symbols as an identifier\u001b[0m\n\u001b[0m     ^\u001b[0m\n\u001b[0;31mSyntaxError\u001b[0m\u001b[0;31m:\u001b[0m invalid syntax\n"
     ]
    }
   ],
   "source": [
    "a@ = 10             #can't use special symbols as an identifier"
   ]
  }
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