3_exception_handling.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {
    "colab_type": "text",
    "id": "m9uJyhSjcOI-"
   },
   "source": [
    "#**Exception Handlilng In Python**"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 0,
   "metadata": {
    "colab": {},
    "colab_type": "code",
    "id": "tsCcaY2NcKPE"
   },
   "outputs": [],
   "source": [
    "def divide_numbers(a,b):\n",
    "  return a/b"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 0,
   "metadata": {
    "colab": {
     "base_uri": "https://localhost:8080/",
     "height": 34
    },
    "colab_type": "code",
    "id": "5MoaYoy0cSTl",
    "outputId": "2043e88d-ed00-4100-9112-f1966c75a216"
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "5.0"
      ]
     },
     "execution_count": 2,
     "metadata": {
      "tags": []
     },
     "output_type": "execute_result"
    }
   ],
   "source": [
    "divide_numbers(10,2)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 0,
   "metadata": {
    "colab": {
     "base_uri": "https://localhost:8080/",
     "height": 233
    },
    "colab_type": "code",
    "id": "pUgT4pjvcTlW",
    "outputId": "967877bc-2d54-4651-b743-1b50f7d8b8b7"
   },
   "outputs": [
    {
     "ename": "ZeroDivisionError",
     "evalue": "ignored",
     "output_type": "error",
     "traceback": [
      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[0;31mZeroDivisionError\u001b[0m                         Traceback (most recent call last)",
      "\u001b[0;32m<ipython-input-3-242ce746b53e>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mdivide_numbers\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;36m10\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;36m0\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[0;32m<ipython-input-1-48dfe4cda1ca>\u001b[0m in \u001b[0;36mdivide_numbers\u001b[0;34m(a, b)\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0;32mdef\u001b[0m \u001b[0mdivide_numbers\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0ma\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0mb\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 2\u001b[0;31m   \u001b[0;32mreturn\u001b[0m \u001b[0ma\u001b[0m\u001b[0;34m/\u001b[0m\u001b[0mb\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[0;31mZeroDivisionError\u001b[0m: division by zero"
     ]
    }
   ],
   "source": [
    "divide_numbers(10,0)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "colab_type": "text",
    "id": "I5m5FdAqcYC2"
   },
   "source": [
    "**Now let's handle the exception in our function**"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "colab": {},
    "colab_type": "code",
    "id": "bd9D7e_TcXE2"
   },
   "outputs": [],
   "source": [
    "def divide_numbers(a,b):\n",
    "  try:\n",
    "    d = a/b\n",
    "  except ZeroDivisionError as e:\n",
    "    print(e)\n",
    "    d = None\n",
    "  return d"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "colab": {
     "base_uri": "https://localhost:8080/",
     "height": 34
    },
    "colab_type": "code",
    "id": "kwaXnur5cdO2",
    "outputId": "50770cfc-e74e-4cbe-c10d-8cbfec492f2f"
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "division by zero\n"
     ]
    }
   ],
   "source": [
    "divide_numbers(10,0)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "colab_type": "text",
    "id": "z2i7SZqxchWJ"
   },
   "source": [
    "### **Handling multiple exceptions**"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 0,
   "metadata": {
    "colab": {
     "base_uri": "https://localhost:8080/",
     "height": 353
    },
    "colab_type": "code",
    "id": "F5qw7hvZcfVO",
    "outputId": "bf9bcf8c-1ae2-44cc-d3e7-a530d5a9bf03"
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Enter number 1:10\n",
      "Enter number 2:5\n"
     ]
    },
    {
     "ename": "TypeError",
     "evalue": "ignored",
     "output_type": "error",
     "traceback": [
      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[0;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
      "\u001b[0;32m<ipython-input-6-688b07b32c86>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0mx\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0minput\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"Enter number 1:\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      2\u001b[0m \u001b[0my\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0minput\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"Enter number 2:\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 3\u001b[0;31m \u001b[0mdivide_numbers\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mx\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0my\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[0;32m<ipython-input-4-ac407cd5be98>\u001b[0m in \u001b[0;36mdivide_numbers\u001b[0;34m(a, b)\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0;32mdef\u001b[0m \u001b[0mdivide_numbers\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0ma\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0mb\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      2\u001b[0m   \u001b[0;32mtry\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 3\u001b[0;31m     \u001b[0md\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0ma\u001b[0m\u001b[0;34m/\u001b[0m\u001b[0mb\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      4\u001b[0m   \u001b[0;32mexcept\u001b[0m \u001b[0mZeroDivisionError\u001b[0m \u001b[0;32mas\u001b[0m \u001b[0me\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      5\u001b[0m     \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0me\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
      "\u001b[0;31mTypeError\u001b[0m: unsupported operand type(s) for /: 'str' and 'str'"
     ]
    }
   ],
   "source": [
    "x=input(\"Enter number 1:\")\n",
    "y=input(\"Enter number 2:\")\n",
    "divide_numbers(x,y)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 0,
   "metadata": {
    "colab": {},
    "colab_type": "code",
    "id": "D3ErIlgdcoDf"
   },
   "outputs": [],
   "source": [
    "def divide_numbers(a,b):\n",
    "  try:\n",
    "    d = a/b\n",
    "  except TypeError as e:\n",
    "    print(e)\n",
    "    d = None\n",
    "  except ZeroDivisionError as e:\n",
    "    print(e)\n",
    "    d = None"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 0,
   "metadata": {
    "colab": {
     "base_uri": "https://localhost:8080/",
     "height": 68
    },
    "colab_type": "code",
    "id": "bxlY5DsAco2_",
    "outputId": "288631e1-fe9a-4b00-dc79-60c23c87da11"
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Enter number 1:10\n",
      "Enter number 2:5\n",
      "unsupported operand type(s) for /: 'str' and 'str'\n"
     ]
    }
   ],
   "source": [
    "x=input(\"Enter number 1:\")\n",
    "y=input(\"Enter number 2:\")\n",
    "divide_numbers(x,y)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "colab_type": "text",
    "id": "NN_9JH7ScuHO"
   },
   "source": [
    "### **Let's make our function fully functional**"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 0,
   "metadata": {
    "colab": {},
    "colab_type": "code",
    "id": "Au5dYzf0cvJ2"
   },
   "outputs": [],
   "source": [
    "def divide_numbers(a,b):\n",
    "  try:\n",
    "    d = float(a)/float(b)\n",
    "  except TypeError as e:\n",
    "    print(e)\n",
    "    d = None\n",
    "  except ZeroDivisionError as e:\n",
    "    print(e)\n",
    "    d = None\n",
    "  return d"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 0,
   "metadata": {
    "colab": {
     "base_uri": "https://localhost:8080/",
     "height": 68
    },
    "colab_type": "code",
    "id": "_V9nZB5ycxEW",
    "outputId": "e438eaf4-c5c0-40da-f47e-cb52d470cebb"
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Enter number 1:10\n",
      "Enter number 2:4\n",
      "2.5\n"
     ]
    }
   ],
   "source": [
    "x=input(\"Enter number 1:\")\n",
    "y=input(\"Enter number 2:\")\n",
    "print(divide_numbers(x,y))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "colab_type": "text",
    "id": "OvJFYYe6c0av"
   },
   "source": [
    "### **Catching all exceptions**"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 0,
   "metadata": {
    "colab": {},
    "colab_type": "code",
    "id": "jpvT7UiZczse"
   },
   "outputs": [],
   "source": [
    "def divide_numbers(a,b):\n",
    "  try:\n",
    "    d = float(a)/float(b)\n",
    "  except Exception as e:\n",
    "    print(\"Exception occured!\")\n",
    "    d = None\n",
    "  return d"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 0,
   "metadata": {
    "colab": {
     "base_uri": "https://localhost:8080/",
     "height": 34
    },
    "colab_type": "code",
    "id": "2-DUM16ic4iG",
    "outputId": "47f719a4-07a6-4e60-d41e-d5276aaa62b1"
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Exception occured!\n"
     ]
    }
   ],
   "source": [
    "divide_numbers(10,0)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 0,
   "metadata": {
    "colab": {
     "base_uri": "https://localhost:8080/",
     "height": 34
    },
    "colab_type": "code",
    "id": "Uq41czmlc51O",
    "outputId": "7a29da69-ff2f-4438-f20f-b71f7ba2b42f"
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Exception occured!\n"
     ]
    }
   ],
   "source": [
    "divide_numbers('abc',0)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "colab_type": "text",
    "id": "y3UfZiYpc8xR"
   },
   "source": [
    "### **Raising exception**"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 0,
   "metadata": {
    "colab": {},
    "colab_type": "code",
    "id": "IKPJB2tIc-d_"
   },
   "outputs": [],
   "source": [
    "def get_grade(score):\n",
    "  if score>70:\n",
    "    return \"A\"\n",
    "  if score>=50 and score<=70:\n",
    "    return \"B\"\n",
    "  if score<50:\n",
    "    return \"C\""
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 0,
   "metadata": {
    "colab": {
     "base_uri": "https://localhost:8080/",
     "height": 34
    },
    "colab_type": "code",
    "id": "SQP_y6c8dATn",
    "outputId": "8e0a0d56-ddbb-498e-ece6-3e75d789c9d2"
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'A'"
      ]
     },
     "execution_count": 15,
     "metadata": {
      "tags": []
     },
     "output_type": "execute_result"
    }
   ],
   "source": [
    "get_grade(90)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 0,
   "metadata": {
    "colab": {
     "base_uri": "https://localhost:8080/",
     "height": 34
    },
    "colab_type": "code",
    "id": "7-0DN04gdBqm",
    "outputId": "5d54497a-09ed-4d74-e3f9-40d41e32d29b"
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'C'"
      ]
     },
     "execution_count": 16,
     "metadata": {
      "tags": []
     },
     "output_type": "execute_result"
    }
   ],
   "source": [
    "get_grade(23)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 0,
   "metadata": {
    "colab": {
     "base_uri": "https://localhost:8080/",
     "height": 34
    },
    "colab_type": "code",
    "id": "vupyGdL1dDfn",
    "outputId": "0a1986c0-b063-4612-c546-c53ee6dfaa24"
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'A'"
      ]
     },
     "execution_count": 17,
     "metadata": {
      "tags": []
     },
     "output_type": "execute_result"
    }
   ],
   "source": [
    "get_grade(200)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "colab_type": "text",
    "id": "aHBCYAGZdEZx"
   },
   "source": [
    "**Here the max test score is 100. So passing 200  as a parameter to this function is clearly invalid. The function should be doing the validation that score should be between 0 to 100 and  raising exception if it is out side this range.**"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 0,
   "metadata": {
    "colab": {},
    "colab_type": "code",
    "id": "nRcuv2mTdGPh"
   },
   "outputs": [],
   "source": [
    "def get_grade(score):\n",
    "  if score<0 or score>100:\n",
    "    raise ValueError(\"Invalid score\")\n",
    "\n",
    "  if score>70:\n",
    "    return \"A\"\n",
    "  if score>=50 and score<=70:\n",
    "    return \"B\"\n",
    "  if score<50:\n",
    "    return \"C\""
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 0,
   "metadata": {
    "colab": {
     "base_uri": "https://localhost:8080/",
     "height": 284
    },
    "colab_type": "code",
    "id": "3XVL5NAydINa",
    "outputId": "06beddb3-488c-4ccb-aacd-b75be902c322"
   },
   "outputs": [
    {
     "ename": "ValueError",
     "evalue": "ignored",
     "output_type": "error",
     "traceback": [
      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[0;31mValueError\u001b[0m                                Traceback (most recent call last)",
      "\u001b[0;32m<ipython-input-19-222f16c44ef8>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mget_grade\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;36m200\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[0;32m<ipython-input-18-2f46eb49eb68>\u001b[0m in \u001b[0;36mget_grade\u001b[0;34m(score)\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0;32mdef\u001b[0m \u001b[0mget_grade\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mscore\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      2\u001b[0m   \u001b[0;32mif\u001b[0m \u001b[0mscore\u001b[0m\u001b[0;34m<\u001b[0m\u001b[0;36m0\u001b[0m \u001b[0;32mor\u001b[0m \u001b[0mscore\u001b[0m\u001b[0;34m>\u001b[0m\u001b[0;36m100\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 3\u001b[0;31m     \u001b[0;32mraise\u001b[0m \u001b[0mValueError\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"Invalid score\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      4\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      5\u001b[0m   \u001b[0;32mif\u001b[0m \u001b[0mscore\u001b[0m\u001b[0;34m>\u001b[0m\u001b[0;36m70\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
      "\u001b[0;31mValueError\u001b[0m: Invalid score"
     ]
    }
   ],
   "source": [
    "get_grade(200)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 0,
   "metadata": {
    "colab": {},
    "colab_type": "code",
    "id": "5C6ZjqordKse"
   },
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "colab_type": "text",
    "id": "nHDUEgzgdMR2"
   },
   "source": [
    "## **Excercise**"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "colab_type": "text",
    "id": "Xwgoad5xdNAv"
   },
   "source": [
    "**1. Write a function that takes file name as an  input and returns the content of that file as an output. You will call this function for a file called idontexist.txt. This file doesn't exist, see what happens when you try to open this file. Now in your function handle file note opening exception and return a message to user saying that this file doesn't exist!**"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "colab_type": "text",
    "id": "KU3Y60iFdOv4"
   },
   "source": [
    "\n",
    "```\n",
    "def get_file_content(file_name):\n",
    "    # your code goes here\n",
    "\n",
    "get_file_content(\"idontexist.txt\")\n",
    "```\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "colab_type": "text",
    "id": "-wgcd9fddQ15"
   },
   "source": [
    "**2. Write a function to calculate area of a triangle. This function takes base and height as parameters and computes triangle area by using formula,**\n",
    "\n",
    "```\n",
    "area = (base*height)/2\n",
    "```\n",
    "**Call this function using string arguments. See what happens. Now change your function such that it throws appropriate exception when data type of base and height is not a number. It should also throw exception when either base or height is negative**"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "colab_type": "text",
    "id": "RGtRqReOdSjO"
   },
   "source": [
    "\n",
    "\n",
    "```\n",
    "def triangle_area(base,height):\n",
    "   # your code goes here\n",
    "\n",
    "triangle_area(20,10) # This works ok\n",
    "triangle_area(\"abc\",10) # This should throw exception saying base value is invalid\n",
    "triangle_area(23,\"\") # This should throw exception saying value of height is invalid\n",
    "triangle_area(-5,10) # This should throw exception saying base value can't be negative\n",
    "triangle_area(8,-3) # Throws exception saying height can't be negative\n",
    "```"
   ]
  }
 ],
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