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{
"metadata": {
"name": "",
"signature": "sha256:44f5daf77255992c95710d94f062b0f1f1e981b9e6cce07f23ed45a322c4b130"
},
"nbformat": 3,
"nbformat_minor": 0,
"worksheets": [
{
"cells": [
{
"cell_type": "heading",
"level": 1,
"metadata": {},
"source": [
"Chapter 14 : Accessing Variable through Pointers"
]
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example: 1, Page Number: 5.107 "
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#Program to accessing through variable pointer\n",
"\n",
"from ctypes import c_int\n",
"\n",
"#Local definition\n",
"a = 22\n",
"a = c_int(a) # ctype datatype declaration\n",
"\n",
"b = 2.25\n",
"b = c_float(b) # ctype datatype declaration\n",
"\n",
"#Pointer variables\n",
"a_po=pointer(a)\n",
"b_po=pointer(b)\n",
"\n",
"# 'id' is a address of letter and it represents the address of the variable\n",
"a = id(a)\n",
"b = id(b)\n",
"\n",
"\n",
"#Result\n",
"print \"\\nValue of a = %d\" %a_po[0]\n",
"print \"\\nValue of b = %.2f\" %b_po[0]\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"\n",
"Value of a = 22\n",
"\n",
"Value of b = 2.25\n"
]
}
],
"prompt_number": 9
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example: 2, Page Number: 5.108"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#Program to print address and value of variable\n",
"\n",
"from ctypes import c_int\n",
"\n",
"#Local definition\n",
"a = 22\n",
"a = c_int(a) # ctype datatype declaration\n",
"\n",
"#Pointer variables\n",
"a_po=pointer(a)\n",
"\n",
"# 'id' is a address of letter and it represents the address of the variable\n",
"a = id(a)\n",
"\n",
"#Result\n",
"print \"\\n Value of a = %d\" %a_po[0]\n",
"print \"\\n Address of a = %u\" %id(a)\n",
"print \"\\n Value at address %u = %d\" %(id(a),a_po[0])\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"\n",
" Value of a = 22\n",
"\n",
" Address of a = 4344066728\n",
"\n",
" Value at address 4344066728 = 22\n"
]
}
],
"prompt_number": 8
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example: 3, Page Number: 5.108"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"# Program to print value and address of variable\n",
"\n",
"from ctypes import c_int\n",
"\n",
"#Local definition\n",
"a = 22\n",
"b = c_int(a) # ctype datatype declaration\n",
"\n",
"#Pointer variable\n",
"b_po=pointer(b)\n",
"\n",
"# 'id' is a address of letter and it represents the address of the variable\n",
"b = id(a)\n",
"\n",
"#Result\n",
"print \"\\n Value of a = %d\" %a\n",
"print \"\\n Value of a = %d\" %(c_int(a).value)\n",
"print \"\\n Value of a = %d\" %b_po[0]\n",
"print \"\\n Address of a = %u\" %id(a)\n",
"print \"\\n Address of a = %u\" %b\n",
"print \"\\n Address of a = %u\" %id(b)\n",
"print \"\\n Value of b = address of a = %u\" %b"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"\n",
" Value of a = 22\n",
"\n",
" Value of a = 22\n",
"\n",
" Value of a = 22\n",
"\n",
" Address of a = 4298180848\n",
"\n",
" Address of a = 4298180848\n",
"\n",
" Address of a = 4344066728\n",
"\n",
" Value of b = address of a = 4298180848\n"
]
}
],
"prompt_number": 10
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example: 4, Page Number: 5.109"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#Program to illustrate pointer to pointer\n",
"\n",
"from ctypes import c_int\n",
"\n",
"#Local definition\n",
"a = 22\n",
"b = c_int(a) # ctype datatype declaration\n",
"c = c_int(a) # ctype datatype declaration\n",
"\n",
"#Pointer variable\n",
"b_po = pointer(b)\n",
"c_po = pointer(b_po) # c_po is a pointer to another pointer\n",
"\n",
"# 'id' is a address of letter and it represents the address of the variable\n",
"b = id(a)\n",
"c = id(b)\n",
"\n",
"#Result\n",
"print \"\\n Value of a is %d\" %a\n",
"print \"\\n Value of a is %d\" %(c_int(a).value)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"\n",
" Value of a is 22\n",
"\n",
" Value of a is 22\n"
]
}
],
"prompt_number": 14
}
],
"metadata": {}
}
]
}
|
