{
"metadata": {
"name": "",
"signature": "sha256:20d38d92a3a25bc02f8bf5fb1b35ef1503e1987dff61d43c4881deab4561fe2c"
},
"nbformat": 3,
"nbformat_minor": 0,
"worksheets": [
{
"cells": [
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<h1>Chapter 19: Run-Time Type ID and the Casting Operators<h1>"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<h3>Example 19.1, Page Number: 453<h3>"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"class myclass:\n",
" pass\n",
"\n",
"#Variable declaration\n",
"i=j=0\n",
"f=0.0\n",
"ob=myclass()\n",
"\n",
"print \"The type of i is:\",type(i).__name__\n",
"print \"The type of f is:\",type(f).__name__\n",
"print \"The type of ob is:\",ob.__class__.__name__\n",
"print \"\\n\"\n",
"\n",
"if type(i)==type(j):\n",
" print \"The types of i and j are the same\"\n",
" \n",
"if not(type(i)==type(f)):\n",
" print \"The types of i and f are not the same\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The type of i is: int\n",
"The type of f is: float\n",
"The type of ob is: myclass\n",
"\n",
"\n",
"The types of i and j are the same\n",
"The types of i and f are not the same\n"
]
}
],
"prompt_number": 2
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<h3>Example 19.2, Page Number: 454<h3>"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"class Base:\n",
" pass\n",
"class Derived1(Base):\n",
" pass\n",
"class Derived2(Base):\n",
" pass\n",
"\n",
"#Variable declaration\n",
"baseob=Base()\n",
"p=[Base()]\n",
"ob1=Derived1()\n",
"ob2=Derived2()\n",
"\n",
"\n",
"p[0]=baseob\n",
"print \"p is pointing to an object of type\",\n",
"print p[0].__class__.__name__\n",
"\n",
"p[0]=ob1\n",
"print \"p is pointing to an object of type\",\n",
"print p[0].__class__.__name__\n",
"\n",
"p[0]=ob2\n",
"print \"p is pointing to an object of type\",\n",
"print p[0].__class__.__name__"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"p is pointing to an object of type Base\n",
"p is pointing to an object of type Derived1\n",
"p is pointing to an object of type Derived2\n"
]
}
],
"prompt_number": 3
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<h3>Example 19.3, Page Number: 455<h3>"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"class Base:\n",
" pass\n",
"class Derived1(Base):\n",
" pass\n",
"class Derived2(Base):\n",
" pass\n",
"\n",
"def WhatType(ob):\n",
" print \"ob is referencing an object of type\",\n",
" print ob.__class__.__name__\n",
" \n",
" \n",
"#Variable declaration\n",
"baseob=Base()\n",
"p=[Base()]\n",
"ob1=Derived1()\n",
"ob2=Derived2()\n",
"\n",
"WhatType(baseob)\n",
"WhatType(ob1)\n",
"WhatType(ob2)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"ob is referencing an object of type Base\n",
"ob is referencing an object of type Derived1\n",
"ob is referencing an object of type Derived2\n"
]
}
],
"prompt_number": 4
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<h3>Example 19.4, Page Number: 456<h3>"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"import random\n",
"\n",
"class figure:\n",
" def __init__(self,i,j):\n",
" self._x=i\n",
" self._y=j\n",
" \n",
"class triangle(figure):\n",
" def __init__(self,i,j):\n",
" figure.__init__(self,i,j)\n",
" def area(self):\n",
" return self._x*0.5*self._y\n",
" \n",
"class rectangle(figure):\n",
" def __init__(self,i,j):\n",
" figure.__init__(self,i,j)\n",
" def area(self):\n",
" return self._x*self._y\n",
" \n",
"class circle(figure):\n",
" def __init__(self,i,j=0):\n",
" figure.__init__(self,i,j)\n",
" def area(self):\n",
" return self._x*self._x*3.14\n",
" \n",
"def factory():\n",
" i=random.randint(0,2)\n",
" if i==0:\n",
" return circle(10.0)\n",
" elif i==1:\n",
" return triangle(10.1,5.3)\n",
" elif i==2:\n",
" return rectangle(4.3,5.7)\n",
" \n",
"\n",
"t=c=r=0 \n",
"p=[None]\n",
"\n",
"#generate and count objects\n",
"for i in range(10):\n",
" p[0]=factory() #generate an object\n",
" print \"Object is \",p[0].__class__.__name__,\". \",\n",
" #count it\n",
" if p[0].__class__.__name__==triangle.__name__:\n",
" t+=1\n",
" if p[0].__class__.__name__==rectangle.__name__:\n",
" r+=1\n",
" if p[0].__class__.__name__==circle.__name__:\n",
" c+=1\n",
" #display its area\n",
" print \"Area is\",p[0].area()\n",
"\n",
"print \"Objects generated:\"\n",
"print \"Triangles:\",t\n",
"print \"Rectangles:\",r\n",
"print \"Circles:\",c"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Object is circle . Area is 314.0\n",
"Object is rectangle . Area is 24.51\n",
"Object is rectangle . Area is 24.51\n",
"Object is circle . Area is 314.0\n",
"Object is rectangle . Area is 24.51\n",
"Object is circle . Area is 314.0\n",
"Object is rectangle . Area is 24.51\n",
"Object is triangle . Area is 26.765\n",
"Object is rectangle . Area is 24.51\n",
"Object is circle . Area is 314.0\n",
"Objects generated:\n",
"Triangles: 1\n",
"Rectangles: 5\n",
"Circles: 4\n"
]
}
],
"prompt_number": 5
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<h3>Example 19.5, Page Number: 456<h3>"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
" \n",
"class myclass:\n",
" def __init__(self,i):\n",
" self.__a=i\n",
" \n",
"o1=myclass(10)\n",
"o2=myclass(9)\n",
"o3=myclass(7.2)\n",
"\n",
"print \"Type of o1 is\",o1.__class__.__name__\n",
"\n",
"print \"Type of o2 is\",o2.__class__.__name__\n",
"\n",
"print \"Type of o3 is\",o3.__class__.__name__\n",
"\n",
"print\n",
"\n",
"if o1.__class__.__name__==o2.__class__.__name__:\n",
" print \"o1 and o2 are the same type\"\n",
" \n",
"if o1.__class__.__name__==o3.__class__.__name__:\n",
" print \"Error\"\n",
"else:\n",
" print \"o1 and o3 are different types\"\n",
"\n",
"#This prints error because python doesnt use templates."
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Type of o1 is myclass\n",
"Type of o2 is myclass\n",
"Type of o3 is myclass\n",
"\n",
"o1 and o2 are the same type\n",
"Error\n"
]
}
],
"prompt_number": 6
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<h3>Example 19.6, Page Number: 460<h3>"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"import random\n",
"\n",
"class figure:\n",
" def __init__(self,i,j):\n",
" self._x=i\n",
" self._y=j\n",
" \n",
"class triangle(figure):\n",
" def __init__(self,i,j):\n",
" figure.__init__(self,i,j)\n",
" def area(self):\n",
" return self._x*0.5*self._y\n",
" \n",
"class rectangle(figure):\n",
" def __init__(self,i,j):\n",
" figure.__init__(self,i,j)\n",
" def area(self):\n",
" return self._x*self._y\n",
" \n",
"class circle(figure):\n",
" def __init__(self,i,j=0):\n",
" figure.__init__(self,i,j)\n",
" def area(self):\n",
" return self._x*self._x*3.14\n",
" \n",
"def factory():\n",
" i=random.randint(0,2)\n",
" if i==0:\n",
" return circle(10.0)\n",
" elif i==1:\n",
" return triangle(10.1,5.3)\n",
" elif i==2:\n",
" return rectangle(4.3,5.7)\n",
" \n",
"\n",
"t=c=r=0 \n",
"p=[None]\n",
"\n",
"#generate and count objects\n",
"for i in range(10):\n",
" p[0]=factory() #generate an object\n",
" print \"Object is \",p[0].__class__.__name__,\". \",\n",
" #count it\n",
" if p[0].__class__.__name__==triangle.__name__:\n",
" t+=1\n",
" if p[0].__class__.__name__==rectangle.__name__:\n",
" r+=1\n",
" if p[0].__class__.__name__==circle.__name__:\n",
" c+=1\n",
" #display its area\n",
" print \"Area is\",p[0].area()\n",
"\n",
"print \"Objects generated:\"\n",
"print \"Triangles:\",t\n",
"print \"Rectangles:\",r\n",
"print \"Circles:\",c"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Object is triangle . Area is 26.765\n",
"Object is circle . Area is 314.0\n",
"Object is circle . Area is 314.0\n",
"Object is rectangle . Area is 24.51\n",
"Object is rectangle . Area is 24.51\n",
"Object is rectangle . Area is 24.51\n",
"Object is circle . Area is 314.0\n",
"Object is circle . Area is 314.0\n",
"Object is rectangle . Area is 24.51\n",
"Object is triangle . Area is 26.765\n",
"Objects generated:\n",
"Triangles: 2\n",
"Rectangles: 4\n",
"Circles: 4\n"
]
}
],
"prompt_number": 7
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<h3>Example 19.7, Page Number: 463<h3>"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"\n",
"class Base:\n",
" def f(self):\n",
" print \"Inside Base\"\n",
" \n",
"class Derived(Base):\n",
" def f(self):\n",
" print \"Inside Derived\"\n",
" \n",
"bp=[Base()] #pointer to base\n",
"b_ob=Base() \n",
"dp=[Derived()] #pointer to derived\n",
"d_ob=Derived()\n",
"\n",
"dp[0]=d_ob\n",
"if dp[0]:\n",
" print \"Cast from Derived * to Derived * OK.\"\n",
" dp[0].f()\n",
"else:\n",
" print \"Error\"\n",
"print\n",
"\n",
"bp[0]=d_ob\n",
"if bp[0]:\n",
" print \"Cast from Derived * to Base * OK.\"\n",
" bp[0].f()\n",
"else:\n",
" print \"Error\"\n",
"print\n",
"\n",
"bp[0]=b_ob\n",
"if bp[0]:\n",
" print \"Cast from Base * to Base * OK.\"\n",
" bp[0].f()\n",
"else:\n",
" print \"Error\"\n",
"print\n",
"\n",
"dp[0]=b_ob\n",
"if dp[0]:\n",
" print \"Error\"\n",
"else:\n",
" print \"Cast from Base * to Derived * not OK.\"\n",
"print\n",
"\n",
"bp[0]=d_ob #bp points to Derived object\n",
"dp[0]=bp[0]\n",
"if dp[0]:\n",
" print \"Cast bp to a Derived * OK.\"\n",
" print \"because bp is really pointing\\n\",\n",
" print \"to a Derived object.\"\n",
" dp[0].f()\n",
"else:\n",
" print \"Error\"\n",
"print\n",
"\n",
"bp[0]=b_ob #bp points to Base object\n",
"dp[0]=bp[0]\n",
"if dp[0]:\n",
" print \"Error\"\n",
"else:\n",
" print \"Now casting bp to a Derived *\\n\",\n",
" print \"is not OK because bp is really\\n\",\n",
" print \" pointing to a Base object.\"\n",
"print\n",
"\n",
"dp[0]=d_ob #dp points to Derived object\n",
"bp[0]=dp[0]\n",
"if bp[0]:\n",
" print \"Casting dp to a Base * is OK.\"\n",
" bp[0].f()\n",
"else:\n",
" print \"Error\"\n",
"print\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Cast from Derived * to Derived * OK.\n",
"Inside Derived\n",
"\n",
"Cast from Derived * to Base * OK.\n",
"Inside Derived\n",
"\n",
"Cast from Base * to Base * OK.\n",
"Inside Base\n",
"\n",
"Error\n",
"\n",
"Cast bp to a Derived * OK.\n",
"because bp is really pointing\n",
"to a Derived object.\n",
"Inside Derived\n",
"\n",
"Error\n",
"\n",
"Casting dp to a Base * is OK.\n",
"Inside Derived\n",
"\n"
]
}
],
"prompt_number": 8
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<h3>Example 19.8, Page Number: 465<h3>"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"\n",
"class Base:\n",
" def f(self):\n",
" pass\n",
" \n",
"class Derived(Base):\n",
" def derivedOnly(self):\n",
" print \"Is a Derived Object\"\n",
" \n",
"bp=[Base()] #pointer to base\n",
"b_ob=Base() \n",
"dp=[Derived()] #pointer to derived\n",
"d_ob=Derived()\n",
"\n",
"#Use typeid\n",
"\n",
"bp[0]=b_ob\n",
"if bp[0].__class__.__name__==Derived.__name__:\n",
" dp[0]=bp[0]\n",
" dp[0].derivedOnly()\n",
"else:\n",
" print \"Cast from Base to Derived failed.\"\n",
" \n",
"bp[0]=d_ob\n",
"if bp[0].__class__.__name__==Derived.__name__:\n",
" dp[0]=bp[0]\n",
" dp[0].derivedOnly()\n",
"else:\n",
" print \"Error, cast should work!\"\n",
" \n",
"#Use dynamic_cast\n",
"\n",
"bp[0]=b_ob\n",
"dp[0]=bp[0]\n",
"if dp[0].__class__.__name__==Derived.__name__:\n",
" dp[0].derivedOnly()\n",
"else:\n",
" print \"Cast from Base to Derived failed.\"\n",
" \n",
"bp[0]=d_ob\n",
"dp[0]=bp[0]\n",
"if dp:\n",
" dp[0].derivedOnly()\n",
"else:\n",
" print \"Error, cast should work!\"\n",
" "
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Cast from Base to Derived failed.\n",
"Is a Derived Object\n",
"Cast from Base to Derived failed.\n",
"Is a Derived Object\n"
]
}
],
"prompt_number": 9
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<h3>Example 19.9, Page Number: 467<h3>"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"def f(p):\n",
" v=p\n",
" v[0]=100\n",
" \n",
"#Variable declaration\n",
"x=[]\n",
"\n",
"x.append(99)\n",
"print \"x before call:\",x[0]\n",
"f(x)\n",
"print \"x after call:\",x[0]\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"x before call: 99\n",
"x after call: 100\n"
]
}
],
"prompt_number": 10
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<h3>Example 19.10, Page Number: 468<h3>"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"\n",
"f=199.22\n",
"\n",
"i=f\n",
"print i\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"199.22\n"
]
}
],
"prompt_number": 11
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<h3>Example 19.11, Page Number: 469<h3>"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"i=0 #int\n",
"p=\"This is a string\"\n",
"\n",
"i=p #cast pointer to integer \n",
"\n",
"#Result\n",
"print i\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"This is a string\n"
]
}
],
"prompt_number": 12
},
{
"cell_type": "code",
"collapsed": false,
"input": [],
"language": "python",
"metadata": {},
"outputs": []
}
],
"metadata": {}
}
]
}