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{
"metadata": {
"name": "Chapter 17"
},
"nbformat": 3,
"nbformat_minor": 0,
"worksheets": [
{
"cells": [
{
"cell_type": "markdown",
"metadata": {},
"source": "<h1>Chapter 17: Exception Handling<h1>"
},
{
"cell_type": "markdown",
"metadata": {},
"source": "<h3>Example 17.1, Page Number: 397<h3>"
},
{
"cell_type": "code",
"collapsed": false,
"input": "'''A simple exception handling example'''\n\nprint \"start\"\n\ntry: #start a try block\n print \"Inside try block\"\n raise Exception(99) #raise an error\n print \"This will not execute\"\nexcept Exception,i: #catch an error\n print \"Caught an exception -- value is:\",\n print i\n\nprint \"end\"",
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": "start\nInside try block\nCaught an exception -- value is: 99\nend\n"
}
],
"prompt_number": 1
},
{
"cell_type": "markdown",
"metadata": {},
"source": "<h3>Example 17.2, Page Number: 399<h3>"
},
{
"cell_type": "code",
"collapsed": false,
"input": "\n'''A simple exception handling example'''\n\nimport sys\n\n\n\ndef main():\n print \"start\"\n try: #start a try block\n print \"Inside try block\"\n raise Exception(99) #raise an error\n print \"This will not execute\"\n except Exception,i: #catch an error\n if isinstance(i,float):\n print \"Caught an exception -- value is:\",\n print i\n else:\n print \"Abnormal program termination\"\n return\n print \"end\"\n\n \nmain()",
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": "start\nInside try block\nAbnormal program termination\n"
}
],
"prompt_number": 1
},
{
"cell_type": "markdown",
"metadata": {},
"source": "<h3>Example 17.3, Page Number: 400<h3>"
},
{
"cell_type": "code",
"collapsed": false,
"input": "'''Throwing an exception from a function called \n from within a try block'''\n\ndef Xtest(test):\n print \"Inside Xtest, test is: \",test\n if(test):\n raise Exception(test)\n \nprint \"start\"\n\ntry: #start a try block\n print \"Inside try block\"\n Xtest(0)\n Xtest(1)\n Xtest(2)\nexcept Exception,i: #catch an error\n print \"Caught an exception -- value is:\",\n print i\n\nprint \"end\"",
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": "start\nInside try block\nInside Xtest, test is: 0\nInside Xtest, test is: 1\nCaught an exception -- value is: 1\nend\n"
}
],
"prompt_number": 2
},
{
"cell_type": "markdown",
"metadata": {},
"source": "<h3>Example 17.4, Page Number: 401<h3>"
},
{
"cell_type": "code",
"collapsed": false,
"input": "'''A try/except is reset each time a function is entered'''\n\ndef Xhandler(test):\n try:\n if(test):\n raise Exception(test)\n except Exception,i:\n print \"Caught One! Ex #:\",i\n \nprint \"start\"\n\nXhandler(1)\nXhandler(2)\nXhandler(0)\nXhandler(3)\n\nprint \"end\"",
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": "start\nCaught One! Ex #: 1\nCaught One! Ex #: 2\nCaught One! Ex #: 3\nend\n"
}
],
"prompt_number": 3
},
{
"cell_type": "markdown",
"metadata": {},
"source": "<h3>Example 17.5, Page Number: 401<h3>"
},
{
"cell_type": "code",
"collapsed": false,
"input": "'''Use exception class'''\n\nclass MyException:\n def __init__(self,s):\n self.str_what=s\n \n#Variable declaration\na=None \nb=None\n\ntry:\n print \"Enter numerator and denominator:\"\n #User-input\n a=10 \n b=0\n if not(b):\n raise MyException(\"Cannot divide by zero!\")\n else:\n print \"Quotient is\",a/b\nexcept MyException as e: #catch an error\n print e.str_what\n ",
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": "Enter numerator and denominator:\nCannot divide by zero!\n"
}
],
"prompt_number": 4
},
{
"cell_type": "markdown",
"metadata": {},
"source": "<h3>Example 17.6, Page Number: 403<h3>"
},
{
"cell_type": "code",
"collapsed": false,
"input": "'''Different types of exceptions being caught'''\n\nclass MyException:\n def __init__(self,s):\n self.x=s\n \ndef Xhandler(test):\n try:\n if(test):\n raise MyException(test)\n else:\n raise MyException(\"Value is zero\")\n except MyException as i:\n if isinstance(i.x,int):\n print \"Caught One! Ex #:\",i.x\n else:\n print \"Caught a string:\",\n print i.x\n \nprint \"start\"\n\nXhandler(1)\nXhandler(2)\nXhandler(0)\nXhandler(3)\n\nprint \"end\"",
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": "start\nCaught One! Ex #: 1\nCaught One! Ex #: 2\nCaught a string: Value is zero\nCaught One! Ex #: 3\nend\n"
}
],
"prompt_number": 5
},
{
"cell_type": "markdown",
"metadata": {},
"source": "<h3>Example 17.7, Page Number: 404<h3>"
},
{
"cell_type": "code",
"collapsed": false,
"input": "'''Catching derived classes'''\n\nclass B:\n pass\n\nclass D(B):\n pass\n\nderived=D()\n\ntry:\n raise B()\nexcept B as b:\n print \"Caught a base class.\"\nexcept D as d:\n print \"This wont execute.\"\n ",
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": "Caught a base class.\n"
}
],
"prompt_number": 6
},
{
"cell_type": "markdown",
"metadata": {},
"source": "<h3>Example 17.8, Page Number: 405<h3>"
},
{
"cell_type": "code",
"collapsed": false,
"input": "'''Example to catch all exceptions'''\n\ndef Xhandler(test):\n try:\n if test==0:\n raise Exception(test) #throw int\n if test==1:\n raise Exception('a') #throw char\n if test==2:\n raise Exception(123.23) #throw double\n except: #Catches all exceptions\n print \"Caught One!\"\n\nprint \"start\"\n\nXhandler(0)\nXhandler(1)\nXhandler(2)\n\nprint \"end\"",
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": "start\nCaught One!\nCaught One!\nCaught One!\nend\n"
}
],
"prompt_number": 7
},
{
"cell_type": "markdown",
"metadata": {},
"source": "<h3>Example 17.9, Page Number: 405<h3>"
},
{
"cell_type": "code",
"collapsed": false,
"input": "'''Example to catch all exceptions'''\n\nclass MyException:\n def __init__(self,s):\n self.x=s\n \ndef Xhandler(test):\n try:\n if test==0:\n raise MyException(test) #throw int\n if test==1:\n raise MyException('a') #throw char\n if test==2:\n raise MyException(123.23) #throw double\n except MyException as i:\n if isinstance(i.x,int): #catch an int exception\n print \"Caught\",i.x \n else: #catch all other exceptions\n print \"Caught One!\"\n \n\nprint \"start\"\n\nXhandler(0)\nXhandler(1)\nXhandler(2)\n\nprint \"end\"",
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": "start\nCaught 0\nCaught One!\nCaught One!\nend\n"
}
],
"prompt_number": 8
},
{
"cell_type": "markdown",
"metadata": {},
"source": "<h3>Example 17.10, Page Number: 407<h3>"
},
{
"cell_type": "code",
"collapsed": false,
"input": "'''Restricting function throw types'''\n\nclass MyException:\n def __init__(self,s):\n self.x=s\n \n#This function can only throw ints, chars and doubles\ndef Xhandler(test):\n if test==0:\n raise MyException(test) #throw int\n if test==1:\n raise MyException('a') #throw char\n if test==2:\n raise MyException(123.23) #throw double\n \n\nprint \"start\"\ntry:\n Xhandler(0)\nexcept MyException as i:\n if isinstance(i.x,int): #catch an int exception\n print \"Caught int\" \n elif isinstance(i.x,str): #catch a char exception\n print \"Caught char\"\n elif isinstance(i.x,float): #catch a float exception\n print \"Caught double\"\n\nprint \"end\"",
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": "start\nCaught int\nend\n"
}
],
"prompt_number": 9
},
{
"cell_type": "markdown",
"metadata": {},
"source": "<h3>Example 17.11, Page Number: 408<h3>"
},
{
"cell_type": "code",
"collapsed": false,
"input": "'''Example of \"rethrowing\" an exception'''\n\ndef Xhandler():\n try:\n raise Exception(\"hello\") #throw a char *\n except Exception,c: #catch a char *\n print \"Caugh char * inside Xhandler\"\n raise #rethrow char * out of function\n \nprint \"start\"\ntry:\n Xhandler()\nexcept Exception,c:\n print \"Caught char * inside main\"\n \nprint \"end\"",
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": "start\nCaugh char * inside Xhandler\nCaught char * inside main\nend\n"
}
],
"prompt_number": 10
},
{
"cell_type": "markdown",
"metadata": {},
"source": "<h3>Example 17.12, Page Number: 410<h3>"
},
{
"cell_type": "code",
"collapsed": false,
"input": "'''Handle exceptions due to allocation failure'''\n\nfrom ctypes import *\n\n#Variable declaration\np=[]\n\ntry:\n for i in range(32):\n p.append(c_int())\nexcept MemoryError,m:\n print \"Allocation failure.\"\n \nfor i in range(32):\n p[i]=i\n \nfor i in range(32):\n print p[i],\n \n ",
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": "0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31\n"
}
],
"prompt_number": 12
},
{
"cell_type": "markdown",
"metadata": {},
"source": "<h3>Example 17.13, Page Number: 410<h3>"
},
{
"cell_type": "code",
"collapsed": false,
"input": "'''Checking allocation failure without raising an exception'''\n\nfrom ctypes import *\n\n#Variable declaration\np=[]\n\n\nfor i in range(32):\n p.append(c_int()) \nif not(p):\n print \"Allocation failure.\"\n \nfor i in range(32):\n p[i]=i\n \nfor i in range(32):\n print p[i],\n \n ",
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": "0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31\n"
}
],
"prompt_number": 13
},
{
"cell_type": "markdown",
"metadata": {},
"source": "<h3>Example 17.13, Page Number: 412<h3>"
},
{
"cell_type": "code",
"collapsed": false,
"input": "'''Demonstrate overloaded new and delete'''\n\nclass three_d:\n def __init__(self,i=0,j=0,k=0): #3=D coordinates\n if(i==0 and j==0 and k==0):\n self.x=self.y=self.z=0\n print \"Constructing 0, 0, 0\"\n else:\n self.x=i\n self.y=j\n self.z=k\n print \"Constructing\",i,\",\",j,\",\",k\n def __del__(self):\n print \"Destructing\"\n #new overloaded relative to three_d.\n def __new__(typ, *args, **kwargs):\n obj = object.__new__(typ, *args, **kwargs)\n return obj\n def show(self):\n print self.x,\",\",\n print self.y,\",\",\n print self.z\n \np1=[]*3\np2=[]\n \ntry:\n print \"Allocating array of three_d objects.\"\n for i in range(3): #allocate array\n p1.append(three_d())\n print \"Allocating three_d object.\"\n p2.append(three_d(5,6,7)) #allocate object\nexcept MemoryError:\n print \"Allocation error\"\n \np1[2].show()\np2[0].show()\n\n\nfor i in xrange(2,-1,-1):\n del p1[i] #delete array\nprint \"Deleting array of thee_d objects.\"\n\ndel p2[0] #delete object\nprint \"Deleting three_d object.\"",
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": "Allocating array of three_d objects.\nConstructing 0, 0, 0\nConstructing 0, 0, 0\nConstructing 0, 0, 0\nAllocating three_d object.\nConstructing 5 , 6 , 7\n0 , 0 , 0\n5 , 6 , 7\nDestructing\nDestructing\nDestructing\nDeleting array of thee_d objects.\nDestructing\nDeleting three_d object.\n"
}
],
"prompt_number": 14
},
{
"cell_type": "code",
"collapsed": false,
"input": "",
"language": "python",
"metadata": {},
"outputs": []
}
],
"metadata": {}
}
]
}
|
