{
"metadata": {
"name": "ch7"
},
"nbformat": 3,
"nbformat_minor": 0,
"worksheets": [
{
"cells": [
{
"cell_type": "heading",
"level": 1,
"metadata": {},
"source": [
"Capter 7: Pointers and References"
]
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.1, Page no: 157"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"\n",
"n=44\n",
"print \"n = \" , n \n",
"# prints the value of n\n",
"print \"&n = \" , hex(id(n)) # prints the address of n\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"n = 44\n",
"&n = 0x8fc0eec\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.2, Page no: 157"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"'''\n",
"Note : Python doesn't support reference/pointer variable. But can be achieved by using mutable datatypes i.e. list.\n",
"'''\n",
"\n",
"\n",
"n = [44]\n",
"rn=n # r is a synonym for n\n",
"print \"n = \" , n , \", rn = \" , rn \n",
"n[0] -= 1\n",
"print \"n = \" , n , \", rn = \" , rn \n",
"rn[0] *= 2\n",
"print \"n = \" , n , \", rn = \" , rn \n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"n = [44] , rn = [44]\n",
"n = [43] , rn = [43]\n",
"n = [86] , rn = [86]\n"
]
}
],
"prompt_number": 2
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.3, Page no: 158"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"n = [44]\n",
"rn=n # r is a synonym for n\n",
"print \"&n = \" , hex(id(n)) , \", rn = \" , hex(id(rn ))\n",
"rn2 = n\n",
"rn3 = rn\n",
"print \"&rn2 = \" , hex(id(rn2)) , \", rn = \" , hex(id(rn ))\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"&n = 0x9c6228c , rn = 0x9c6228c\n",
"&rn2 = 0x9c6228c , rn = 0x9c6228c\n"
]
}
],
"prompt_number": 3
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.4, Page no: 159"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"\n",
"n = [44]\n",
"print \"n = \" , n , \", &n = \" , hex(id(n))\n",
"pn = n\n",
"print \"pn = \" , hex(id(pn)) , \", &pn = \" , hex(id(hex(id(pn))))\n",
"\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"n = [44] , &n = 0x9c624ec\n",
"pn = 0x9c624ec , &pn = 0x9c6aa60\n"
]
}
],
"prompt_number": 4
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.5, Page no: 159"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"\n",
"n = [44]\n",
"print \"n = \" , n , \", &n = \" , hex(id(n))\n",
"pn = n\n",
"print \"\\tpn = \" , hex(id(pn)) , \",\\n &pn = \" , hex(id(hex(id(pn))))\n",
"print \"*pn = \" , pn\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"n = [44] , &n = 0x9c58d6c\n",
"\tpn = 0x9c58d6c ,\n",
" &pn = 0x9c6ab20\n",
"*pn = [44]\n"
]
}
],
"prompt_number": 5
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.6, Page no: 160"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"\n",
"n = [44]\n",
"print \"n = \" , n , \", &n = \" , hex(id(n))\n",
"pn = n\n",
"print \"\\tpn = \" , hex(id(pn)) , \",\\n &pn = \" , hex(id(hex(id(pn))))\n",
"print \"*pn = \" , pn\n",
"ppn = pn\n",
"\n",
"print \" ppn = \" , hex(id(hex(id(ppn)))) \n",
"print \" &ppn = \" , hex(id(hex(id(hex(id(ppn))))))\n",
"print \" *ppn = \" , hex(id(ppn)) \n",
"print \"**ppn = \" , ppn \n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"n = [44] , &n = 0x9bf05ac\n",
"\tpn = 0x9bf05ac ,\n",
" &pn = 0x9c58160\n",
"*pn = [44]\n",
" ppn = 0x9c58680\n",
" &ppn = 0x9c58160\n",
" *ppn = 0x9bf05ac\n",
"**ppn = [44]\n"
]
}
],
"prompt_number": 6
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.7, Page no: 160"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"\n",
"n = [44]\n",
"print \"n = \" , n , \"\\n &n = \" , hex(id(n))\n",
"pn = n\n",
"print \"\\tpn = \" , hex(id(pn)) , \",\\n &pn = \" , hex(id(hex(id(pn))))\n",
"print \"*pn = \" , pn\n",
"nn = pn\n",
"print \" ppn = \" , hex(id(nn))\n",
"print \" &ppn = \" , hex(id(hex(id(nn))))\n",
"rpn = pn\n",
"print \" ppn = \" , hex(id(rpn))\n",
"print \" &ppn = \" , hex(id(hex(id(rpn))))\n",
"\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"n = [44] \n",
" &n = 0x9bf60ec\n",
"\tpn = 0x9bf60ec ,\n",
" &pn = 0x9bf0e40\n",
"*pn = [44]\n",
" ppn = 0x9bf60ec\n",
" &ppn = 0x9bf0e40\n",
" ppn = 0x9bf60ec\n",
" &ppn = 0x9bf0f20\n"
]
}
],
"prompt_number": 7
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.8, Page no: 162"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"\n",
"def max_(m,n):\n",
" if m>n:\n",
" return m\n",
" else:\n",
" return n\n",
"\n",
"m = 44\n",
"n = 22\n",
"print m , \", \" , n , \", \" , max_(m,n)\n",
"m = max_(m,n) \n",
"m = 55\n",
"# changes the value of m from 44 to 55\n",
"print m , \", \" , n , \", \" , max_(m,n) \n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"44 , 22 , 44\n",
"55 , 22 , 55\n"
]
}
],
"prompt_number": 8
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.9, Page no: 163"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"\n",
"v = []\n",
"for k in range(1,5):\n",
" v.append(1.0/k)\n",
"\n",
"for i in range(4):\n",
" print \"v[\" , i , \"] = \" , v[i]\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"v[ 0 ] = 1.0\n",
"v[ 1 ] = 0.5\n",
"v[ 2 ] = 0.333333333333\n",
"v[ 3 ] = 0.25\n"
]
}
],
"prompt_number": 9
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.10, Page no: 163"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"import sys\n",
"a = [22, 33, 44]\n",
"\n",
"print \"a = \" , hex(id(a))\n",
"print \"sizeof(int) = \" , sys.getsizeof(1) \n",
"s = 0\n",
"for i in a:\n",
" s += i\n",
" print \"\\t i = \" , hex(id(i)),\n",
" print \"\\t *i = \" , i,\n",
" print \"\\t sum = \" , s\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"a = 0x9bf688c\n",
"sizeof(int) = 12\n",
"\t i = 0x8fc0ff4 \t *i = 22 \t sum = 22\n",
"\t i = 0x8fc0f70 \t *i = 33 \t sum = 55\n",
"\t i = 0x8fc0eec \t *i = 44 \t sum = 99\n"
]
}
],
"prompt_number": 10
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.11, Page no: 165"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"\n",
"a = [22, 33, 44, 55, 66]\n",
"print \"a = \" , hex(id(a)) , \", *a = \" , a[0] \n",
"for p in a:\n",
" print \"p = \" , hex(id(p)) , \", *p = \" , p \n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"a = 0x9c6526c , *a = 22\n",
"p = 0x8fc0ff4 , *p = 22\n",
"p = 0x8fc0f70 , *p = 33\n",
"p = 0x8fc0eec , *p = 44\n",
"p = 0x8fc0e68 , *p = 55\n",
"p = 0x8fc0de4 , *p = 66\n"
]
}
],
"prompt_number": 11
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.12, Page no: 165"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"def loc(a1,a2,n1,n2):\n",
" p = []\n",
" for element in a2:\n",
" if element in a1:\n",
" p.append(element)\n",
" return p\n",
"\n",
"a1 = [11, 11, 11, 11, 11, 22, 33, 44, 55]\n",
"a2 = [11, 11, 11, 22, 33]\n",
"print \"Array a1 begins at location\\t\" , hex(id(a1 ))\n",
"print \"Array a2 begins at location\\t\" , hex(id(a2)) \n",
"p = loc(a1, a2, 9, 5)\n",
"if (p):\n",
" print \"Array a2 found at location\\t\" , hex(id(p))\n",
" for i in range(len(p)):\n",
" print \"\\t\" , hex(id(p[i])) , \": \" , p[i], \"\\t\" , hex(id(a2[i])) , \": \" , a2[i] \n",
"else:\n",
" print \"Not found.\"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Array a1 begins at location\t0x9bea56c\n",
"Array a2 begins at location\t0x9bea62c\n",
"Array a2 found at location\t0x9bea6cc\n",
"\t0x8fc1078 : 11 \t0x8fc1078 : 11\n",
"\t0x8fc1078 : 11 \t0x8fc1078 : 11\n",
"\t0x8fc1078 : 11 \t0x8fc1078 : 11\n",
"\t0x8fc0ff4 : 22 \t0x8fc0ff4 : 22\n",
"\t0x8fc0f70 : 33 \t0x8fc0f70 : 33\n"
]
}
],
"prompt_number": 12
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.13, Page no: 166"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"\n",
"def get(a):\n",
" print \"Enter number of items: \"\n",
" n = int(raw_input())\n",
" print \"Enter \" , n , \" items, one per line:\"\n",
" for i in range(n):\n",
" print \"\\t\" , i+1 , \": \",\n",
" a.append(float(raw_input()))\n",
"\n",
"def print_(a):\n",
" for i in range(len(a)):\n",
" print a[i] ,\n",
" print ''\n",
"\n",
"a = []\n",
"get(a)\n",
"print_(a)\n",
"a = []\n",
"get(a)\n",
"print_(a)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Enter number of items: \n"
]
},
{
"name": "stdout",
"output_type": "stream",
"stream": "stdout",
"text": [
"4\n"
]
},
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Enter 4 items, one per line:\n",
"\t1 : "
]
},
{
"name": "stdout",
"output_type": "stream",
"stream": "stdout",
"text": [
"44.4\n"
]
},
{
"output_type": "stream",
"stream": "stdout",
"text": [
" \t2 : "
]
},
{
"name": "stdout",
"output_type": "stream",
"stream": "stdout",
"text": [
"77.7\n"
]
},
{
"output_type": "stream",
"stream": "stdout",
"text": [
" \t3 : "
]
},
{
"name": "stdout",
"output_type": "stream",
"stream": "stdout",
"text": [
"22.2\n"
]
},
{
"output_type": "stream",
"stream": "stdout",
"text": [
" \t4 : "
]
},
{
"name": "stdout",
"output_type": "stream",
"stream": "stdout",
"text": [
"88.8\n"
]
},
{
"output_type": "stream",
"stream": "stdout",
"text": [
" 44.4 77.7 22.2 88.8 \n",
"Enter number of items: \n"
]
},
{
"name": "stdout",
"output_type": "stream",
"stream": "stdout",
"text": [
"2\n"
]
},
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Enter 2 items, one per line:\n",
"\t1 : "
]
},
{
"name": "stdout",
"output_type": "stream",
"stream": "stdout",
"text": [
"3.33\n"
]
},
{
"output_type": "stream",
"stream": "stdout",
"text": [
" \t2 : "
]
},
{
"name": "stdout",
"output_type": "stream",
"stream": "stdout",
"text": [
"9.99\n"
]
},
{
"output_type": "stream",
"stream": "stdout",
"text": [
" 3.33 9.99 \n"
]
}
],
"prompt_number": 13
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.14, Page no: 167"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"\n",
"def sort(p, n):\n",
" for i in range(1,n):\n",
" for j in range(n-i):\n",
" if (p[j] > p[j+1]):\n",
" p[j],p[j+1] = p[j+1],p[j]\n"
],
"language": "python",
"metadata": {},
"outputs": [],
"prompt_number": 14
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 7.15, Page no: 168"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"\n",
"def sum_(k,n):\n",
" # returns the sum f(0) + f(1) + f(2) + . . . + f(n-1):\n",
" s = 0\n",
" for i in range(1,n+1):\n",
" s += k(i)\n",
" return s\n",
"\n",
"def square(k):\n",
" return k*k\n",
"\n",
"def cube(k):\n",
" return k*k*k\n",
"\n",
"\n",
"print sum_(square,4) # 1 + 4 + 9 + 16\n",
"print sum_(cube,4) # 1 + 8 + 27 + 64\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"30\n",
"100\n"
]
}
],
"prompt_number": 15
}
],
"metadata": {}
}
]
}