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2 <head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>Chapter. list_tuples</title><link rel="stylesheet" href="/review/support/styles.css" type="text/css" /><meta name="generator" content="DocBook XSL Stylesheets V1.74.3" /><link rel="shortcut icon" type="image/png" href="/review/support/figs/favicon.png" /><script type="text/javascript" src="/review/support/jquery-min.js"></script><script type="text/javascript" src="/review/support/form.js"></script><script type="text/javascript" src="/review/support/hsbook.js"></script></head> |
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3 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="chapter" id="ch3list_tuples"> |
4 <title> |
4 <div class="titlepage"></div> |
5 Chapter. list_tuples |
5 <div class="toc"> |
6 </title> |
6 <p><b>Table of Contents</b></p> |
7 <link rel="stylesheet" href="/review/support/styles.css" type="text/css" /> |
7 <dl> |
8 <meta name="generator" content="DocBook XSL Stylesheets V1.74.3" /> |
8 <dt><span class="article"><a href="#id2896388">Lists and Tuples</a></span></dt> |
9 <link rel="shortcut icon" type="image/png" href="/review/support/figs/favicon.png" /> |
9 <dd><dl> |
10 <script type="text/javascript" src="/review/support/jquery-min.js"> |
10 <dt><span class="section"><a href="#id2706433">1. Lists</a></span></dt> |
11 </script> |
11 <dd><dl> |
12 <script type="text/javascript" src="/review/support/form.js"> |
12 <dt><span class="section"><a href="#id2896192">1.1. Common List Operations</a></span></dt> |
13 </script> |
13 <dt><span class="section"><a href="#id2947658">1.2. None, Empty Lists, and Initialization</a></span></dt> |
14 <script type="text/javascript" src="/review/support/hsbook.js"> |
14 <dt><span class="section"><a href="#id2947698">1.3. Nested Lists</a></span></dt> |
15 </script> |
15 <dt><span class="section"><a href="#id2947732">1.4. List Methods</a></span></dt> |
16 </head> |
16 </dl></dd> |
17 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> |
17 <dt><span class="section"><a href="#id2948048">2. Tuples</a></span></dt> |
18 <div class="chapter" id="ch3list_tuples"> |
18 <dd><dl><dt><span class="section"><a href="#id2948145">2.1. Common Tuple Operations</a></span></dt></dl></dd> |
19 <div class="titlepage"> |
19 <dt><span class="section"><a href="#id2948295">3. Additional Syntax</a></span></dt> |
20 </div> |
20 <dd><dl> |
21 <div class="toc"> |
21 <dt><span class="section"><a href="#id2948312">3.1. range()</a></span></dt> |
22 <p> |
22 <dt><span class="section"><a href="#id2948344">3.2. for</a></span></dt> |
23 <b> |
23 </dl></dd> |
24 Table of Contents |
24 <dt><span class="section"><a href="#id2948403">4. Conclusion</a></span></dt> |
25 </b> |
25 </dl></dd> |
26 </p> |
26 </dl> |
27 <dl> |
27 </div> |
28 <dt> |
28 <div class="article" title="Lists and Tuples"> |
29 <span class="article"> |
29 <div class="titlepage"> |
30 <a href="#id2951820"> |
30 <div><div><h2 class="title"> |
31 Lists and Tuples |
31 <a name="id2896388"></a>Lists and Tuples</h2></div></div> |
32 </a> |
32 <hr /> |
33 </span> |
33 </div> |
34 </dt> |
34 <div class="toc"> |
35 <dd> |
35 <p><b>Table of Contents</b></p> |
36 <dl> |
36 <dl> |
37 <dt> |
37 <dt><span class="section"><a href="#id2706433">1. Lists</a></span></dt> |
38 <span class="section"> |
38 <dd><dl> |
39 <a href="#id2761866"> |
39 <dt><span class="section"><a href="#id2896192">1.1. Common List Operations</a></span></dt> |
40 1. Lists |
40 <dt><span class="section"><a href="#id2947658">1.2. None, Empty Lists, and Initialization</a></span></dt> |
41 </a> |
41 <dt><span class="section"><a href="#id2947698">1.3. Nested Lists</a></span></dt> |
42 </span> |
42 <dt><span class="section"><a href="#id2947732">1.4. List Methods</a></span></dt> |
43 </dt> |
43 </dl></dd> |
44 <dd> |
44 <dt><span class="section"><a href="#id2948048">2. Tuples</a></span></dt> |
45 <dl> |
45 <dd><dl><dt><span class="section"><a href="#id2948145">2.1. Common Tuple Operations</a></span></dt></dl></dd> |
46 <dt> |
46 <dt><span class="section"><a href="#id2948295">3. Additional Syntax</a></span></dt> |
47 <span class="section"> |
47 <dd><dl> |
48 <a href="#id2951624"> |
48 <dt><span class="section"><a href="#id2948312">3.1. range()</a></span></dt> |
49 1.1. Common List Operations |
49 <dt><span class="section"><a href="#id2948344">3.2. for</a></span></dt> |
50 </a> |
50 </dl></dd> |
51 </span> |
51 <dt><span class="section"><a href="#id2948403">4. Conclusion</a></span></dt> |
52 </dt> |
52 </dl> |
53 <dt> |
53 </div> |
54 <span class="section"> |
54 <div class="section" title="1.Lists"> |
55 <a href="#id3003090"> |
55 <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
56 1.2. None, Empty Lists, and Initialization |
56 <a name="id2706433"></a>1.Lists</h2></div></div></div> |
57 </a> |
57 <p id="ch3list_tuples_1">Python provides an intuitive way to represent a group items, called <span class="emphasis"><em>Lists</em></span>. The |
58 </span> |
58 items of a <span class="emphasis"><em>List</em></span> are called its elements. Unlike C/C++, elements can be of any |
59 </dt> |
59 type. A <span class="emphasis"><em>List</em></span> is represented as a list of comma-sepated elements with square |
60 <dt> |
60 brackets around them:</p> |
61 <span class="section"> |
61 <pre class="programlisting"> |
62 <a href="#id3003130"> |
62 >>> a = [10, 'Python programming', 20.3523, 23, 3534534L] |
63 1.3. Nested Lists |
63 >>> a |
64 </a> |
64 [10, 'Python programming', 20.3523, 23, 3534534L]</pre> |
65 </span> |
65 <div class="section" title="1.1.Common List Operations"> |
66 </dt> |
66 <div class="titlepage"><div><div><h3 class="title"> |
67 <dt> |
67 <a name="id2896192"></a>1.1.Common List Operations</h3></div></div></div> |
68 <span class="section"> |
68 <p id="ch3list_tuples_2">The following are some of the most commonly used operations on <span class="emphasis"><em>Lists</em></span>.</p> |
69 <a href="#id3003165"> |
69 <div class="section" title="1.1.1.Indexing"> |
70 1.4. List Methods |
70 <div class="titlepage"><div><div><h4 class="title"> |
71 </a> |
71 <a name="id2896236"></a>1.1.1.Indexing</h4></div></div></div> |
72 </span> |
72 <p id="ch3list_tuples_3">Individual elements of a <span class="emphasis"><em>List</em></span> can be accessed using an index to the element. |
73 </dt> |
73 The indices start at 0. One can also access the elements of the <span class="emphasis"><em>List</em></span> in reverse |
74 </dl> |
74 using negative indices.:</p> |
75 </dd> |
75 <pre class="programlisting"> |
76 <dt> |
76 >>> a[1] |
77 <span class="section"> |
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78 <a href="#id3003481"> |
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79 2. Tuples |
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80 </a> |
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81 </span> |
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82 </dt> |
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83 <dd> |
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84 <dl> |
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85 <dt> |
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86 <span class="section"> |
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87 <a href="#id3003578"> |
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88 2.1. Common Tuple Operations |
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89 </a> |
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90 </span> |
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91 </dt> |
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92 </dl> |
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93 </dd> |
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94 <dt> |
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95 <span class="section"> |
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96 <a href="#id3003727"> |
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97 3. Additional Syntax |
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98 </a> |
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99 </span> |
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100 </dt> |
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101 <dd> |
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102 <dl> |
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103 <dt> |
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104 <span class="section"> |
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105 <a href="#id3003745"> |
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106 3.1. range() |
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107 </a> |
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108 </span> |
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109 </dt> |
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110 <dt> |
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111 <span class="section"> |
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112 <a href="#id3003777"> |
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113 3.2. for |
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114 </a> |
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115 </span> |
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116 </dt> |
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117 </dl> |
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118 </dd> |
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119 <dt> |
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120 <span class="section"> |
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121 <a href="#id3003836"> |
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122 4. Conclusion |
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123 </a> |
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124 </span> |
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125 </dt> |
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126 </dl> |
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127 </dd> |
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128 </dl> |
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129 </div> |
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130 <div class="article" title="Lists and Tuples"> |
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131 <div class="titlepage"> |
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132 <div> |
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133 <div> |
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134 <h2 class="title"> |
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135 <a name="id2951820"> |
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136 </a> |
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137 Lists and Tuples |
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138 </h2> |
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139 </div> |
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140 </div> |
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141 <hr /> |
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142 </div> |
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143 <div class="toc"> |
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144 <p> |
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145 <b> |
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146 Table of Contents |
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147 </b> |
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148 </p> |
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149 <dl> |
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150 <dt> |
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151 <span class="section"> |
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152 <a href="#id2761866"> |
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153 1. Lists |
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154 </a> |
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155 </span> |
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156 </dt> |
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157 <dd> |
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158 <dl> |
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159 <dt> |
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160 <span class="section"> |
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161 <a href="#id2951624"> |
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162 1.1. Common List Operations |
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163 </a> |
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164 </span> |
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165 </dt> |
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166 <dt> |
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167 <span class="section"> |
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168 <a href="#id3003090"> |
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169 1.2. None, Empty Lists, and Initialization |
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170 </a> |
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171 </span> |
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172 </dt> |
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173 <dt> |
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174 <span class="section"> |
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175 <a href="#id3003130"> |
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176 1.3. Nested Lists |
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177 </a> |
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178 </span> |
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179 </dt> |
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180 <dt> |
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181 <span class="section"> |
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182 <a href="#id3003165"> |
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183 1.4. List Methods |
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184 </a> |
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185 </span> |
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186 </dt> |
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187 </dl> |
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188 </dd> |
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189 <dt> |
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190 <span class="section"> |
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191 <a href="#id3003481"> |
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192 2. Tuples |
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193 </a> |
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194 </span> |
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195 </dt> |
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196 <dd> |
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197 <dl> |
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198 <dt> |
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199 <span class="section"> |
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200 <a href="#id3003578"> |
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201 2.1. Common Tuple Operations |
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202 </a> |
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203 </span> |
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204 </dt> |
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205 </dl> |
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206 </dd> |
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207 <dt> |
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208 <span class="section"> |
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209 <a href="#id3003727"> |
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210 3. Additional Syntax |
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211 </a> |
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212 </span> |
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213 </dt> |
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214 <dd> |
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215 <dl> |
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216 <dt> |
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217 <span class="section"> |
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218 <a href="#id3003745"> |
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219 3.1. range() |
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220 </a> |
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221 </span> |
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222 </dt> |
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223 <dt> |
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224 <span class="section"> |
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225 <a href="#id3003777"> |
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226 3.2. for |
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227 </a> |
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228 </span> |
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229 </dt> |
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230 </dl> |
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231 </dd> |
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232 <dt> |
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233 <span class="section"> |
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234 <a href="#id3003836"> |
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235 4. Conclusion |
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236 </a> |
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237 </span> |
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238 </dt> |
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239 </dl> |
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240 </div> |
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241 <div class="section" title="1.Lists"> |
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242 <div class="titlepage"> |
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243 <div> |
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244 <div> |
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245 <h2 class="title" style="clear: both"> |
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246 <a name="id2761866"> |
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247 </a> |
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248 1.Lists |
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249 </h2> |
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250 </div> |
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251 </div> |
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252 </div> |
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253 <p id="ch3list_tuples_1"> |
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254 Python provides an intuitive way to represent a group items, called |
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255 <span class="emphasis"> |
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256 <em> |
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257 Lists |
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258 </em> |
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259 </span> |
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260 . The |
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261 items of a |
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262 <span class="emphasis"> |
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263 <em> |
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264 List |
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265 </em> |
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266 </span> |
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267 are called its elements. Unlike C/C++, elements can be of any |
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268 type. A |
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269 <span class="emphasis"> |
|
270 <em> |
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271 List |
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272 </em> |
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273 </span> |
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274 is represented as a list of comma-sepated elements with square |
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275 brackets around them: |
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276 </p> |
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277 <pre class="programlisting"> |
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278 >>> a = [10, 'Python programming', 20.3523, 23, 3534534L] |
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279 >>> a |
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280 [10, 'Python programming', 20.3523, 23, 3534534L] |
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281 </pre> |
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282 <div class="section" title="1.1.Common List Operations"> |
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283 <div class="titlepage"> |
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284 <div> |
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285 <div> |
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286 <h3 class="title"> |
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287 <a name="id2951624"> |
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288 </a> |
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289 1.1.Common List Operations |
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290 </h3> |
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291 </div> |
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292 </div> |
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293 </div> |
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294 <p id="ch3list_tuples_2"> |
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295 The following are some of the most commonly used operations on |
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296 <span class="emphasis"> |
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297 <em> |
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298 Lists |
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299 </em> |
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300 </span> |
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301 . |
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302 </p> |
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303 <div class="section" title="1.1.1.Indexing"> |
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304 <div class="titlepage"> |
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305 <div> |
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306 <div> |
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307 <h4 class="title"> |
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308 <a name="id2951669"> |
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309 </a> |
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310 1.1.1.Indexing |
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311 </h4> |
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312 </div> |
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313 </div> |
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314 </div> |
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315 <p id="ch3list_tuples_3"> |
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316 Individual elements of a |
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317 <span class="emphasis"> |
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318 <em> |
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319 List |
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320 </em> |
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321 </span> |
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322 can be accessed using an index to the element. |
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323 The indices start at 0. One can also access the elements of the |
|
324 <span class="emphasis"> |
|
325 <em> |
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326 List |
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327 </em> |
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328 </span> |
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329 in reverse |
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330 using negative indices.: |
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331 </p> |
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332 <pre class="programlisting"> |
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333 >>> a[1] |
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334 'Python programming' |
77 'Python programming' |
335 >>> a[-1] |
78 >>> a[-1] |
336 3534534L |
79 3534534L</pre> |
337 </pre> |
80 <p id="ch3list_tuples_4">It is important to note here that the last element of the <span class="emphasis"><em>List</em></span> has an index of |
338 <p id="ch3list_tuples_4"> |
81 -1.</p> |
339 It is important to note here that the last element of the |
82 </div> |
340 <span class="emphasis"> |
83 <div class="section" title="1.1.2.Concatenating"> |
341 <em> |
84 <div class="titlepage"><div><div><h4 class="title"> |
342 List |
85 <a name="id2947372"></a>1.1.2.Concatenating</h4></div></div></div> |
343 </em> |
86 <p id="ch3list_tuples_5">Two or more <span class="emphasis"><em>Lists</em></span> can be concatenated using the + operator:</p> |
344 </span> |
87 <pre class="programlisting"> |
345 has an index of |
88 >>> a + ['foo', 12, 23.3432, 54] |
346 -1. |
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347 </p> |
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348 </div> |
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349 <div class="section" title="1.1.2.Concatenating"> |
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350 <div class="titlepage"> |
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351 <div> |
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352 <div> |
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353 <h4 class="title"> |
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354 <a name="id3002805"> |
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355 </a> |
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356 1.1.2.Concatenating |
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357 </h4> |
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358 </div> |
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359 </div> |
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360 </div> |
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361 <p id="ch3list_tuples_5"> |
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362 Two or more |
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363 <span class="emphasis"> |
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364 <em> |
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365 Lists |
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366 </em> |
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367 </span> |
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368 can be concatenated using the + operator: |
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369 </p> |
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370 <pre class="programlisting"> |
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371 >>> a + ['foo', 12, 23.3432, 54] |
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372 [10, 'Python programming', 20.3523, 'foo', 12, 23.3432, 54] |
89 [10, 'Python programming', 20.3523, 'foo', 12, 23.3432, 54] |
373 >>> [54, 75, 23] + ['write', 67, 'read'] |
90 >>> [54, 75, 23] + ['write', 67, 'read'] |
374 [54, 75, 23, 'write', 67, 'read'] |
91 [54, 75, 23, 'write', 67, 'read']</pre> |
375 </pre> |
92 </div> |
376 </div> |
93 <div class="section" title="1.1.3.Slicing"> |
377 <div class="section" title="1.1.3.Slicing"> |
94 <div class="titlepage"><div><div><h4 class="title"> |
378 <div class="titlepage"> |
95 <a name="id2947393"></a>1.1.3.Slicing</h4></div></div></div> |
379 <div> |
96 <p id="ch3list_tuples_6">A <span class="emphasis"><em>List</em></span> can be sliced off to contain a subset of elements of the <span class="emphasis"><em>List</em></span>. Slicing |
380 <div> |
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381 <h4 class="title"> |
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382 <a name="id3002825"> |
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383 </a> |
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384 1.1.3.Slicing |
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385 </h4> |
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386 </div> |
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387 </div> |
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388 </div> |
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389 <p id="ch3list_tuples_6"> |
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390 A |
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391 <span class="emphasis"> |
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392 <em> |
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393 List |
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394 </em> |
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395 </span> |
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396 can be sliced off to contain a subset of elements of the |
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397 <span class="emphasis"> |
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398 <em> |
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399 List |
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400 </em> |
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401 </span> |
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402 . Slicing |
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403 can be done by using two indices separated by a colon, where the first index is |
97 can be done by using two indices separated by a colon, where the first index is |
404 inclusive and the second index is exclusive. The resulting slice is also a |
98 inclusive and the second index is exclusive. The resulting slice is also a <span class="emphasis"><em>List</em></span>.:</p> |
405 <span class="emphasis"> |
99 <pre class="programlisting"> |
406 <em> |
100 >>> num = [1, 2, 3, 4, 5, 6, 7, 8, 9] |
407 List |
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408 </em> |
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409 </span> |
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410 .: |
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411 </p> |
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412 <pre class="programlisting"> |
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413 >>> num = [1, 2, 3, 4, 5, 6, 7, 8, 9] |
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414 >>> num[3:6] |
101 >>> num[3:6] |
415 [4, 5, 6] |
102 [4, 5, 6] |
416 >>> num[0:1] |
103 >>> num[0:1] |
417 [1] |
104 [1] |
418 >>> num[7:10] |
105 >>> num[7:10] |
419 [7, 8, 9] |
106 [7, 8, 9]</pre> |
420 </pre> |
107 <p id="ch3list_tuples_7">The last example showed how to access last 3 elements of the <span class="emphasis"><em>List</em></span>. There is a |
421 <p id="ch3list_tuples_7"> |
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422 The last example showed how to access last 3 elements of the |
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423 <span class="emphasis"> |
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424 <em> |
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425 List |
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426 </em> |
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427 </span> |
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428 . There is a |
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429 small catch here. The second index 10 actually refers to the 11th element of the |
108 small catch here. The second index 10 actually refers to the 11th element of the |
430 <span class="emphasis"> |
109 <span class="emphasis"><em>List</em></span> which is still valid, even though it doesn't exist because the second |
431 <em> |
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432 List |
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433 </em> |
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434 </span> |
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435 which is still valid, even though it doesn't exist because the second |
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436 index is exclusive and tells the Python interpreter to get the last element of |
110 index is exclusive and tells the Python interpreter to get the last element of |
437 the |
111 the <span class="emphasis"><em>List</em></span>. But this can also be done in a much easier way using negative indices:</p> |
438 <span class="emphasis"> |
112 <pre class="programlisting"> |
439 <em> |
113 >>> num[-3:-1] |
440 List |
114 [7, 8, 9]</pre> |
441 </em> |
115 <p id="ch3list_tuples_8">Excluding the first index implies that the slice must start at the beginning of |
442 </span> |
116 the <span class="emphasis"><em>List</em></span>, while excluding the second index includes all the elements till the |
443 . But this can also be done in a much easier way using negative indices: |
117 end of the <span class="emphasis"><em>List</em></span>. A third parameter to a slice, which is implicitly taken as 1 |
444 </p> |
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445 <pre class="programlisting"> |
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446 >>> num[-3:-1] |
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447 [7, 8, 9] |
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448 </pre> |
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449 <p id="ch3list_tuples_8"> |
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450 Excluding the first index implies that the slice must start at the beginning of |
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451 the |
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452 <span class="emphasis"> |
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453 <em> |
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454 List |
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455 </em> |
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456 </span> |
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457 , while excluding the second index includes all the elements till the |
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458 end of the |
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459 <span class="emphasis"> |
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460 <em> |
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461 List |
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462 </em> |
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463 </span> |
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464 . A third parameter to a slice, which is implicitly taken as 1 |
|
465 is the step of the slice. It is specified as a value which follows a colon after |
118 is the step of the slice. It is specified as a value which follows a colon after |
466 the second index: |
119 the second index:</p> |
467 </p> |
120 <pre class="programlisting"> |
468 <pre class="programlisting"> |
121 >>> num[:4] |
469 >>> num[:4] |
|
470 [1, 2, 3, 4] |
122 [1, 2, 3, 4] |
471 >>> num[7:] |
123 >>> num[7:] |
472 [8, 9] |
124 [8, 9] |
473 >>> num[-3:] |
125 >>> num[-3:] |
474 [7, 8, 9] |
126 [7, 8, 9] |
477 >>> num[4:9:3] |
129 >>> num[4:9:3] |
478 [5, 8] |
130 [5, 8] |
479 >>> num[3::2] |
131 >>> num[3::2] |
480 [4, 6, 8] |
132 [4, 6, 8] |
481 >>> num[::4] |
133 >>> num[::4] |
482 [1, 5, 9] |
134 [1, 5, 9]</pre> |
483 </pre> |
135 </div> |
484 </div> |
136 <div class="section" title="1.1.4.Multiplication"> |
485 <div class="section" title="1.1.4.Multiplication"> |
137 <div class="titlepage"><div><div><h4 class="title"> |
486 <div class="titlepage"> |
138 <a name="id2947472"></a>1.1.4.Multiplication</h4></div></div></div> |
487 <div> |
139 <p id="ch3list_tuples_9">A <span class="emphasis"><em>List</em></span> can be multiplied with an integer to repeat itself:</p> |
488 <div> |
140 <pre class="programlisting"> |
489 <h4 class="title"> |
141 >>> [20] * 5 |
490 <a name="id3002905"> |
|
491 </a> |
|
492 1.1.4.Multiplication |
|
493 </h4> |
|
494 </div> |
|
495 </div> |
|
496 </div> |
|
497 <p id="ch3list_tuples_9"> |
|
498 A |
|
499 <span class="emphasis"> |
|
500 <em> |
|
501 List |
|
502 </em> |
|
503 </span> |
|
504 can be multiplied with an integer to repeat itself: |
|
505 </p> |
|
506 <pre class="programlisting"> |
|
507 >>> [20] * 5 |
|
508 [20, 20, 20, 20, 20] |
142 [20, 20, 20, 20, 20] |
509 >>> [42, 'Python', 54] * 3 |
143 >>> [42, 'Python', 54] * 3 |
510 [42, 'Python', 54, 42, 'Python', 54, 42, 'Python', 54] |
144 [42, 'Python', 54, 42, 'Python', 54, 42, 'Python', 54]</pre> |
511 </pre> |
145 </div> |
512 </div> |
146 <div class="section" title="1.1.5.Membership"> |
513 <div class="section" title="1.1.5.Membership"> |
147 <div class="titlepage"><div><div><h4 class="title"> |
514 <div class="titlepage"> |
148 <a name="id2947497"></a>1.1.5.Membership</h4></div></div></div> |
515 <div> |
149 <p id="ch3list_tuples_a"><span class="strong"><strong>in</strong></span> operator is used to find whether an element is part of the <span class="emphasis"><em>List</em></span>. It |
516 <div> |
150 returns <span class="strong"><strong>True</strong></span> if the element is present in the <span class="emphasis"><em>List</em></span> or <span class="strong"><strong>False</strong></span> if it is not |
517 <h4 class="title"> |
|
518 <a name="id3002929"> |
|
519 </a> |
|
520 1.1.5.Membership |
|
521 </h4> |
|
522 </div> |
|
523 </div> |
|
524 </div> |
|
525 <p id="ch3list_tuples_a"> |
|
526 <span class="strong"> |
|
527 <strong> |
|
528 in |
|
529 </strong> |
|
530 </span> |
|
531 operator is used to find whether an element is part of the |
|
532 <span class="emphasis"> |
|
533 <em> |
|
534 List |
|
535 </em> |
|
536 </span> |
|
537 . It |
|
538 returns |
|
539 <span class="strong"> |
|
540 <strong> |
|
541 True |
|
542 </strong> |
|
543 </span> |
|
544 if the element is present in the |
|
545 <span class="emphasis"> |
|
546 <em> |
|
547 List |
|
548 </em> |
|
549 </span> |
|
550 or |
|
551 <span class="strong"> |
|
552 <strong> |
|
553 False |
|
554 </strong> |
|
555 </span> |
|
556 if it is not |
|
557 present. Since this operator returns a Boolean value it is called a Boolean |
151 present. Since this operator returns a Boolean value it is called a Boolean |
558 operator: |
152 operator:</p> |
559 </p> |
153 <pre class="programlisting"> |
560 <pre class="programlisting"> |
154 >>> names = ['Guido', 'Alex', 'Tim'] |
561 >>> names = ['Guido', 'Alex', 'Tim'] |
|
562 >>> 'Tim' in names |
155 >>> 'Tim' in names |
563 True |
156 True |
564 >>> 'Adam' in names |
157 >>> 'Adam' in names |
565 False |
158 False</pre> |
566 </pre> |
159 </div> |
567 </div> |
160 <div class="section" title="1.1.6.Length, Maximum and Minimum"> |
568 <div class="section" title="1.1.6.Length, Maximum and Minimum"> |
161 <div class="titlepage"><div><div><h4 class="title"> |
569 <div class="titlepage"> |
162 <a name="id2947539"></a>1.1.6.Length, Maximum and Minimum</h4></div></div></div> |
570 <div> |
163 <p id="ch3list_tuples_b">Length of a <span class="emphasis"><em>List</em></span> can be found out using the len function. The max function |
571 <div> |
|
572 <h4 class="title"> |
|
573 <a name="id3002972"> |
|
574 </a> |
|
575 1.1.6.Length, Maximum and Minimum |
|
576 </h4> |
|
577 </div> |
|
578 </div> |
|
579 </div> |
|
580 <p id="ch3list_tuples_b"> |
|
581 Length of a |
|
582 <span class="emphasis"> |
|
583 <em> |
|
584 List |
|
585 </em> |
|
586 </span> |
|
587 can be found out using the len function. The max function |
|
588 returns the element with the largest value and the min function returns the |
164 returns the element with the largest value and the min function returns the |
589 element with the smallest value: |
165 element with the smallest value:</p> |
590 </p> |
166 <pre class="programlisting"> |
591 <pre class="programlisting"> |
167 >>> num = [4, 1, 32, 12, 67, 34, 65] |
592 >>> num = [4, 1, 32, 12, 67, 34, 65] |
|
593 >>> len(num) |
168 >>> len(num) |
594 7 |
169 7 |
595 >>> max(num) |
170 >>> max(num) |
596 67 |
171 67 |
597 >>> min(num) |
172 >>> min(num) |
598 1 |
173 1</pre> |
599 </pre> |
174 </div> |
600 </div> |
175 <div class="section" title="1.1.7.Changing Elements"> |
601 <div class="section" title="1.1.7.Changing Elements"> |
176 <div class="titlepage"><div><div><h4 class="title"> |
602 <div class="titlepage"> |
177 <a name="id2947564"></a>1.1.7.Changing Elements</h4></div></div></div> |
603 <div> |
178 <p id="ch3list_tuples_c">Unlike Strings <span class="emphasis"><em>Lists</em></span> are mutable, i.e. elements of a <span class="emphasis"><em>List</em></span> can be manipulated:</p> |
604 <div> |
179 <pre class="programlisting"> |
605 <h4 class="title"> |
180 >>> a = [1, 3, 5, 7] |
606 <a name="id3002997"> |
|
607 </a> |
|
608 1.1.7.Changing Elements |
|
609 </h4> |
|
610 </div> |
|
611 </div> |
|
612 </div> |
|
613 <p id="ch3list_tuples_c"> |
|
614 Unlike Strings |
|
615 <span class="emphasis"> |
|
616 <em> |
|
617 Lists |
|
618 </em> |
|
619 </span> |
|
620 are mutable, i.e. elements of a |
|
621 <span class="emphasis"> |
|
622 <em> |
|
623 List |
|
624 </em> |
|
625 </span> |
|
626 can be manipulated: |
|
627 </p> |
|
628 <pre class="programlisting"> |
|
629 >>> a = [1, 3, 5, 7] |
|
630 >>> a[2] = 9 |
181 >>> a[2] = 9 |
631 >>> a |
182 >>> a |
632 [1, 3, 9, 7] |
183 [1, 3, 9, 7]</pre> |
633 </pre> |
184 </div> |
634 </div> |
185 <div class="section" title="1.1.8.Deleting Elements"> |
635 <div class="section" title="1.1.8.Deleting Elements"> |
186 <div class="titlepage"><div><div><h4 class="title"> |
636 <div class="titlepage"> |
187 <a name="id2947590"></a>1.1.8.Deleting Elements</h4></div></div></div> |
637 <div> |
188 <p id="ch3list_tuples_d">An element or a slice of a <span class="emphasis"><em>List</em></span> can be deleted by using the <span class="strong"><strong>del</strong></span> statement:</p> |
638 <div> |
189 <pre class="programlisting"> |
639 <h4 class="title"> |
190 >>> a = [1, 3, 5, 7, 9, 11] |
640 <a name="id3003022"> |
|
641 </a> |
|
642 1.1.8.Deleting Elements |
|
643 </h4> |
|
644 </div> |
|
645 </div> |
|
646 </div> |
|
647 <p id="ch3list_tuples_d"> |
|
648 An element or a slice of a |
|
649 <span class="emphasis"> |
|
650 <em> |
|
651 List |
|
652 </em> |
|
653 </span> |
|
654 can be deleted by using the |
|
655 <span class="strong"> |
|
656 <strong> |
|
657 del |
|
658 </strong> |
|
659 </span> |
|
660 statement: |
|
661 </p> |
|
662 <pre class="programlisting"> |
|
663 >>> a = [1, 3, 5, 7, 9, 11] |
|
664 >>> del a[-2:] |
191 >>> del a[-2:] |
665 >>> a |
192 >>> a |
666 [1, 3, 5, 7] |
193 [1, 3, 5, 7] |
667 >>> del a[1] |
194 >>> del a[1] |
668 >>> a |
195 >>> a |
669 [1, 5, 7] |
196 [1, 5, 7]</pre> |
670 </pre> |
197 </div> |
671 </div> |
198 <div class="section" title="1.1.9.Assign to Slices"> |
672 <div class="section" title="1.1.9.Assign to Slices"> |
199 <div class="titlepage"><div><div><h4 class="title"> |
673 <div class="titlepage"> |
200 <a name="id2947617"></a>1.1.9.Assign to Slices</h4></div></div></div> |
674 <div> |
201 <p id="ch3list_tuples_e">In the same way, values can be assigned to individual elements of the <span class="emphasis"><em>List</em></span>, |
675 <div> |
202 a <span class="emphasis"><em>List</em></span> of elements can be assigned to a slice:</p> |
676 <h4 class="title"> |
203 <pre class="programlisting"> |
677 <a name="id3003050"> |
204 >>> a = [2, 3, 4, 5] |
678 </a> |
|
679 1.1.9.Assign to Slices |
|
680 </h4> |
|
681 </div> |
|
682 </div> |
|
683 </div> |
|
684 <p id="ch3list_tuples_e"> |
|
685 In the same way, values can be assigned to individual elements of the |
|
686 <span class="emphasis"> |
|
687 <em> |
|
688 List |
|
689 </em> |
|
690 </span> |
|
691 , |
|
692 a |
|
693 <span class="emphasis"> |
|
694 <em> |
|
695 List |
|
696 </em> |
|
697 </span> |
|
698 of elements can be assigned to a slice: |
|
699 </p> |
|
700 <pre class="programlisting"> |
|
701 >>> a = [2, 3, 4, 5] |
|
702 >>> a[:2] = [0, 1] |
205 >>> a[:2] = [0, 1] |
703 [0, 1, 4, 5] |
206 [0, 1, 4, 5] |
704 >>> a[2:2] = [2, 3] |
207 >>> a[2:2] = [2, 3] |
705 >>> a |
208 >>> a |
706 [0, 1, 2, 3, 4, 5] |
209 [0, 1, 2, 3, 4, 5] |
707 >>> a[2:4] = [] |
210 >>> a[2:4] = [] |
708 >>> a |
211 >>> a |
709 [0, 1, 4, 5] |
212 [0, 1, 4, 5]</pre> |
710 </pre> |
213 <p id="ch3list_tuples_f">The last two examples should be particularly noted carefully. The last but one |
711 <p id="ch3list_tuples_f"> |
214 example insert elements or a list of elements into a <span class="emphasis"><em>List</em></span> and the last example |
712 The last two examples should be particularly noted carefully. The last but one |
215 deletes a list of elements from the <span class="emphasis"><em>List</em></span>.</p> |
713 example insert elements or a list of elements into a |
216 </div> |
714 <span class="emphasis"> |
217 </div> |
715 <em> |
218 <div class="section" title="1.2.None, Empty Lists, and Initialization"> |
716 List |
219 <div class="titlepage"><div><div><h3 class="title"> |
717 </em> |
220 <a name="id2947658"></a>1.2.None, Empty Lists, and Initialization</h3></div></div></div> |
718 </span> |
221 <p id="ch3list_tuples_10">An <span class="emphasis"><em>Empty List</em></span> is a <span class="emphasis"><em>List</em></span> with no elements and is simply represented as |
719 and the last example |
222 []. A <span class="emphasis"><em>None List</em></span> is one with all elements in it being <span class="strong"><strong>None</strong></span>. It serves |
720 deletes a list of elements from the |
|
721 <span class="emphasis"> |
|
722 <em> |
|
723 List |
|
724 </em> |
|
725 </span> |
|
726 . |
|
727 </p> |
|
728 </div> |
|
729 </div> |
|
730 <div class="section" title="1.2.None, Empty Lists, and Initialization"> |
|
731 <div class="titlepage"> |
|
732 <div> |
|
733 <div> |
|
734 <h3 class="title"> |
|
735 <a name="id3003090"> |
|
736 </a> |
|
737 1.2.None, Empty Lists, and Initialization |
|
738 </h3> |
|
739 </div> |
|
740 </div> |
|
741 </div> |
|
742 <p id="ch3list_tuples_10"> |
|
743 An |
|
744 <span class="emphasis"> |
|
745 <em> |
|
746 Empty List |
|
747 </em> |
|
748 </span> |
|
749 is a |
|
750 <span class="emphasis"> |
|
751 <em> |
|
752 List |
|
753 </em> |
|
754 </span> |
|
755 with no elements and is simply represented as |
|
756 []. A |
|
757 <span class="emphasis"> |
|
758 <em> |
|
759 None List |
|
760 </em> |
|
761 </span> |
|
762 is one with all elements in it being |
|
763 <span class="strong"> |
|
764 <strong> |
|
765 None |
|
766 </strong> |
|
767 </span> |
|
768 . It serves |
|
769 the purpose having a container list of some fixed number of elements with |
223 the purpose having a container list of some fixed number of elements with |
770 no value: |
224 no value:</p> |
771 </p> |
225 <pre class="programlisting"> |
772 <pre class="programlisting"> |
226 >>> a = [] |
773 >>> a = [] |
|
774 >>> a |
227 >>> a |
775 [] |
228 [] |
776 >>> n = [None] * 10 |
229 >>> n = [None] * 10 |
777 >>> n |
230 >>> n |
778 [None, None, None, None, None, None, None, None, None, None] |
231 [None, None, None, None, None, None, None, None, None, None]</pre> |
779 </pre> |
232 </div> |
780 </div> |
233 <div class="section" title="1.3.Nested Lists"> |
781 <div class="section" title="1.3.Nested Lists"> |
234 <div class="titlepage"><div><div><h3 class="title"> |
782 <div class="titlepage"> |
235 <a name="id2947698"></a>1.3.Nested Lists</h3></div></div></div> |
783 <div> |
236 <p id="ch3list_tuples_11">As mentioned earlier, a List can contain elements of any data type. This also |
784 <div> |
237 implies a <span class="emphasis"><em>List</em></span> can have a <span class="emphasis"><em>Lists</em></span> themselves as its elements. These are |
785 <h3 class="title"> |
238 called as <span class="emphasis"><em>Nested Lists</em></span>. There is no limit on the depth of the <span class="emphasis"><em>Nested Lists</em></span>:</p> |
786 <a name="id3003130"> |
239 <pre class="programlisting"> |
787 </a> |
240 >>> a = [1, [1, 2, 3], 3, [1, [1, 2, 3]], 7]</pre> |
788 1.3.Nested Lists |
241 </div> |
789 </h3> |
242 <div class="section" title="1.4.List Methods"> |
790 </div> |
243 <div class="titlepage"><div><div><h3 class="title"> |
791 </div> |
244 <a name="id2947732"></a>1.4.List Methods</h3></div></div></div> |
792 </div> |
245 <p id="ch3list_tuples_12">A method is a function that is coupled to an object. More about objects |
793 <p id="ch3list_tuples_11"> |
|
794 As mentioned earlier, a List can contain elements of any data type. This also |
|
795 implies a |
|
796 <span class="emphasis"> |
|
797 <em> |
|
798 List |
|
799 </em> |
|
800 </span> |
|
801 can have a |
|
802 <span class="emphasis"> |
|
803 <em> |
|
804 Lists |
|
805 </em> |
|
806 </span> |
|
807 themselves as its elements. These are |
|
808 called as |
|
809 <span class="emphasis"> |
|
810 <em> |
|
811 Nested Lists |
|
812 </em> |
|
813 </span> |
|
814 . There is no limit on the depth of the |
|
815 <span class="emphasis"> |
|
816 <em> |
|
817 Nested Lists |
|
818 </em> |
|
819 </span> |
|
820 : |
|
821 </p> |
|
822 <pre class="programlisting"> |
|
823 >>> a = [1, [1, 2, 3], 3, [1, [1, 2, 3]], 7] |
|
824 </pre> |
|
825 </div> |
|
826 <div class="section" title="1.4.List Methods"> |
|
827 <div class="titlepage"> |
|
828 <div> |
|
829 <div> |
|
830 <h3 class="title"> |
|
831 <a name="id3003165"> |
|
832 </a> |
|
833 1.4.List Methods |
|
834 </h3> |
|
835 </div> |
|
836 </div> |
|
837 </div> |
|
838 <p id="ch3list_tuples_12"> |
|
839 A method is a function that is coupled to an object. More about objects |
|
840 and its methods are discussed in Advanced Python module. In general, a |
246 and its methods are discussed in Advanced Python module. In general, a |
841 method is called like: |
247 method is called like:</p> |
842 </p> |
248 <pre class="programlisting"> |
843 <pre class="programlisting"> |
249 object.method(arguments)</pre> |
844 object.method(arguments) |
250 <p id="ch3list_tuples_13">For now, it is enough to know that a list of elements is an object and |
845 </pre> |
251 so <span class="emphasis"><em>List</em></span> methods can be called upon them. Also some of the methods change |
846 <p id="ch3list_tuples_13"> |
252 the <span class="emphasis"><em>List</em></span> in-place, meaning it modifies the existing list instead of creating |
847 For now, it is enough to know that a list of elements is an object and |
|
848 so |
|
849 <span class="emphasis"> |
|
850 <em> |
|
851 List |
|
852 </em> |
|
853 </span> |
|
854 methods can be called upon them. Also some of the methods change |
|
855 the |
|
856 <span class="emphasis"> |
|
857 <em> |
|
858 List |
|
859 </em> |
|
860 </span> |
|
861 in-place, meaning it modifies the existing list instead of creating |
|
862 a new one, while other methods don't. It must be noted as we run through |
253 a new one, while other methods don't. It must be noted as we run through |
863 the |
254 the <span class="emphasis"><em>List</em></span> methods.</p> |
864 <span class="emphasis"> |
255 <p id="ch3list_tuples_14">Some of the most commonly used <span class="emphasis"><em>List</em></span> methods are as follows:</p> |
865 <em> |
256 <div class="section" title="1.4.1.append"> |
866 List |
257 <div class="titlepage"><div><div><h4 class="title"> |
867 </em> |
258 <a name="id2947779"></a>1.4.1.append</h4></div></div></div> |
868 </span> |
259 <p id="ch3list_tuples_15">The <span class="emphasis"><em>append</em></span> method is used to append an object at the end of the list:</p> |
869 methods. |
260 <pre class="programlisting"> |
870 </p> |
261 >>> prime = [2, 3, 5] |
871 <p id="ch3list_tuples_14"> |
|
872 Some of the most commonly used |
|
873 <span class="emphasis"> |
|
874 <em> |
|
875 List |
|
876 </em> |
|
877 </span> |
|
878 methods are as follows: |
|
879 </p> |
|
880 <div class="section" title="1.4.1.append"> |
|
881 <div class="titlepage"> |
|
882 <div> |
|
883 <div> |
|
884 <h4 class="title"> |
|
885 <a name="id3003212"> |
|
886 </a> |
|
887 1.4.1.append |
|
888 </h4> |
|
889 </div> |
|
890 </div> |
|
891 </div> |
|
892 <p id="ch3list_tuples_15"> |
|
893 The |
|
894 <span class="emphasis"> |
|
895 <em> |
|
896 append |
|
897 </em> |
|
898 </span> |
|
899 method is used to append an object at the end of the list: |
|
900 </p> |
|
901 <pre class="programlisting"> |
|
902 >>> prime = [2, 3, 5] |
|
903 >>> prime.append(7) |
262 >>> prime.append(7) |
904 >>> prime |
263 >>> prime |
905 [2, 3, 5, 7] |
264 [2, 3, 5, 7]</pre> |
906 </pre> |
265 <p id="ch3list_tuples_16">It is important to note that append changes the <span class="emphasis"><em>List</em></span> in-place.</p> |
907 <p id="ch3list_tuples_16"> |
266 </div> |
908 It is important to note that append changes the |
267 <div class="section" title="1.4.2.count"> |
909 <span class="emphasis"> |
268 <div class="titlepage"><div><div><h4 class="title"> |
910 <em> |
269 <a name="id2947808"></a>1.4.2.count</h4></div></div></div> |
911 List |
270 <p id="ch3list_tuples_17">The <span class="emphasis"><em>count</em></span> method returns the number of occurences of a particular element |
912 </em> |
271 in a list:</p> |
913 </span> |
272 <pre class="programlisting"> |
914 in-place. |
273 >>> [1, 4, 4, 9, 9, 9].count(9) |
915 </p> |
|
916 </div> |
|
917 <div class="section" title="1.4.2.count"> |
|
918 <div class="titlepage"> |
|
919 <div> |
|
920 <div> |
|
921 <h4 class="title"> |
|
922 <a name="id3003241"> |
|
923 </a> |
|
924 1.4.2.count |
|
925 </h4> |
|
926 </div> |
|
927 </div> |
|
928 </div> |
|
929 <p id="ch3list_tuples_17"> |
|
930 The |
|
931 <span class="emphasis"> |
|
932 <em> |
|
933 count |
|
934 </em> |
|
935 </span> |
|
936 method returns the number of occurences of a particular element |
|
937 in a list: |
|
938 </p> |
|
939 <pre class="programlisting"> |
|
940 >>> [1, 4, 4, 9, 9, 9].count(9) |
|
941 3 |
274 3 |
942 >>> tlst = ['Python', 'is', 'a', 'beautiful', 'language'] |
275 >>> tlst = ['Python', 'is', 'a', 'beautiful', 'language'] |
943 >>> tlst.count('Python') |
276 >>> tlst.count('Python') |
944 1 |
277 1</pre> |
945 </pre> |
278 </div> |
946 </div> |
279 <div class="section" title="1.4.3.extend"> |
947 <div class="section" title="1.4.3.extend"> |
280 <div class="titlepage"><div><div><h4 class="title"> |
948 <div class="titlepage"> |
281 <a name="id2947831"></a>1.4.3.extend</h4></div></div></div> |
949 <div> |
282 <p id="ch3list_tuples_18">The <span class="emphasis"><em>extend</em></span> method extends the list on which it is called by the list supplied |
950 <div> |
283 as argument to it:</p> |
951 <h4 class="title"> |
284 <pre class="programlisting"> |
952 <a name="id3003264"> |
285 >>> a = [1, 2, 3] |
953 </a> |
|
954 1.4.3.extend |
|
955 </h4> |
|
956 </div> |
|
957 </div> |
|
958 </div> |
|
959 <p id="ch3list_tuples_18"> |
|
960 The |
|
961 <span class="emphasis"> |
|
962 <em> |
|
963 extend |
|
964 </em> |
|
965 </span> |
|
966 method extends the list on which it is called by the list supplied |
|
967 as argument to it: |
|
968 </p> |
|
969 <pre class="programlisting"> |
|
970 >>> a = [1, 2, 3] |
|
971 >>> b = [4, 5, 6] |
286 >>> b = [4, 5, 6] |
972 >>> a.extend(b) |
287 >>> a.extend(b) |
973 [1, 2, 3, 4, 5, 6] |
288 [1, 2, 3, 4, 5, 6]</pre> |
974 </pre> |
289 <p id="ch3list_tuples_19">This is an in-place method. This method is equivalent to using the + operator, but |
975 <p id="ch3list_tuples_19"> |
290 using the + operator returns a new list.</p> |
976 This is an in-place method. This method is equivalent to using the + operator, but |
291 </div> |
977 using the + operator returns a new list. |
292 <div class="section" title="1.4.4.index"> |
978 </p> |
293 <div class="titlepage"><div><div><h4 class="title"> |
979 </div> |
294 <a name="id2947859"></a>1.4.4.index</h4></div></div></div> |
980 <div class="section" title="1.4.4.index"> |
295 <p id="ch3list_tuples_1a">The <span class="emphasis"><em>index</em></span> method returns the index position of the element in the list |
981 <div class="titlepage"> |
296 specified as argument:</p> |
982 <div> |
297 <pre class="programlisting"> |
983 <div> |
298 >>> a = [1, 2, 3, ,4, 5] |
984 <h4 class="title"> |
|
985 <a name="id3003292"> |
|
986 </a> |
|
987 1.4.4.index |
|
988 </h4> |
|
989 </div> |
|
990 </div> |
|
991 </div> |
|
992 <p id="ch3list_tuples_1a"> |
|
993 The |
|
994 <span class="emphasis"> |
|
995 <em> |
|
996 index |
|
997 </em> |
|
998 </span> |
|
999 method returns the index position of the element in the list |
|
1000 specified as argument: |
|
1001 </p> |
|
1002 <pre class="programlisting"> |
|
1003 >>> a = [1, 2, 3, ,4, 5] |
|
1004 >>> a.index(4) |
299 >>> a.index(4) |
1005 3 |
300 3</pre> |
1006 </pre> |
301 </div> |
1007 </div> |
302 <div class="section" title="1.4.5.insert"> |
1008 <div class="section" title="1.4.5.insert"> |
303 <div class="titlepage"><div><div><h4 class="title"> |
1009 <div class="titlepage"> |
304 <a name="id2947879"></a>1.4.5.insert</h4></div></div></div> |
1010 <div> |
305 <p id="ch3list_tuples_1b">The <span class="emphasis"><em>insert</em></span> method is used to insert an element specified as the second |
1011 <div> |
306 argument to the list at the position specified by the first argument:</p> |
1012 <h4 class="title"> |
307 <pre class="programlisting"> |
1013 <a name="id3003311"> |
308 >>> a = ['Python', 'is', 'cool'] |
1014 </a> |
|
1015 1.4.5.insert |
|
1016 </h4> |
|
1017 </div> |
|
1018 </div> |
|
1019 </div> |
|
1020 <p id="ch3list_tuples_1b"> |
|
1021 The |
|
1022 <span class="emphasis"> |
|
1023 <em> |
|
1024 insert |
|
1025 </em> |
|
1026 </span> |
|
1027 method is used to insert an element specified as the second |
|
1028 argument to the list at the position specified by the first argument: |
|
1029 </p> |
|
1030 <pre class="programlisting"> |
|
1031 >>> a = ['Python', 'is', 'cool'] |
|
1032 >>> a.insert(2, 'so') |
309 >>> a.insert(2, 'so') |
1033 >>> a |
310 >>> a |
1034 ['Python', 'is', 'so', 'cool'] |
311 ['Python', 'is', 'so', 'cool']</pre> |
1035 </pre> |
312 <p id="ch3list_tuples_1c">The <span class="emphasis"><em>insert</em></span> method changes the <span class="emphasis"><em>List</em></span> in-place.</p> |
1036 <p id="ch3list_tuples_1c"> |
313 </div> |
1037 The |
314 <div class="section" title="1.4.6.pop"> |
1038 <span class="emphasis"> |
315 <div class="titlepage"><div><div><h4 class="title"> |
1039 <em> |
316 <a name="id2947913"></a>1.4.6.pop</h4></div></div></div> |
1040 insert |
317 <p id="ch3list_tuples_1d">The <span class="emphasis"><em>pop</em></span> method removes an element from the list. The index position |
1041 </em> |
|
1042 </span> |
|
1043 method changes the |
|
1044 <span class="emphasis"> |
|
1045 <em> |
|
1046 List |
|
1047 </em> |
|
1048 </span> |
|
1049 in-place. |
|
1050 </p> |
|
1051 </div> |
|
1052 <div class="section" title="1.4.6.pop"> |
|
1053 <div class="titlepage"> |
|
1054 <div> |
|
1055 <div> |
|
1056 <h4 class="title"> |
|
1057 <a name="id3003346"> |
|
1058 </a> |
|
1059 1.4.6.pop |
|
1060 </h4> |
|
1061 </div> |
|
1062 </div> |
|
1063 </div> |
|
1064 <p id="ch3list_tuples_1d"> |
|
1065 The |
|
1066 <span class="emphasis"> |
|
1067 <em> |
|
1068 pop |
|
1069 </em> |
|
1070 </span> |
|
1071 method removes an element from the list. The index position |
|
1072 of the element to be removed can be specified as an argument to the |
318 of the element to be removed can be specified as an argument to the |
1073 <span class="emphasis"> |
319 <span class="emphasis"><em>pop</em></span> method, if not it removes the last element by default:</p> |
1074 <em> |
320 <pre class="programlisting"> |
1075 pop |
321 >>> a = [1, 2, 3, 4, 5] |
1076 </em> |
|
1077 </span> |
|
1078 method, if not it removes the last element by default: |
|
1079 </p> |
|
1080 <pre class="programlisting"> |
|
1081 >>> a = [1, 2, 3, 4, 5] |
|
1082 >>> a.pop() |
322 >>> a.pop() |
1083 >>> a |
323 >>> a |
1084 5 |
324 5 |
1085 >>> a.pop(2) |
325 >>> a.pop(2) |
1086 >>> a |
326 >>> a |
1087 3 |
327 3</pre> |
1088 </pre> |
328 <p id="ch3list_tuples_1e">The <span class="emphasis"><em>pop</em></span> method changes the <span class="emphasis"><em>List</em></span> in-place.</p> |
1089 <p id="ch3list_tuples_1e"> |
329 </div> |
1090 The |
330 <div class="section" title="1.4.7.remove"> |
1091 <span class="emphasis"> |
331 <div class="titlepage"><div><div><h4 class="title"> |
1092 <em> |
332 <a name="id2947951"></a>1.4.7.remove</h4></div></div></div> |
1093 pop |
333 <p id="ch3list_tuples_1f">The <span class="emphasis"><em>remove</em></span> method removes the first occurence of an element supplied as a |
1094 </em> |
334 parameter:</p> |
1095 </span> |
335 <pre class="programlisting"> |
1096 method changes the |
336 >>> a = [1, 2, 3, 4, 2, 5, 2] |
1097 <span class="emphasis"> |
|
1098 <em> |
|
1099 List |
|
1100 </em> |
|
1101 </span> |
|
1102 in-place. |
|
1103 </p> |
|
1104 </div> |
|
1105 <div class="section" title="1.4.7.remove"> |
|
1106 <div class="titlepage"> |
|
1107 <div> |
|
1108 <div> |
|
1109 <h4 class="title"> |
|
1110 <a name="id3003383"> |
|
1111 </a> |
|
1112 1.4.7.remove |
|
1113 </h4> |
|
1114 </div> |
|
1115 </div> |
|
1116 </div> |
|
1117 <p id="ch3list_tuples_1f"> |
|
1118 The |
|
1119 <span class="emphasis"> |
|
1120 <em> |
|
1121 remove |
|
1122 </em> |
|
1123 </span> |
|
1124 method removes the first occurence of an element supplied as a |
|
1125 parameter: |
|
1126 </p> |
|
1127 <pre class="programlisting"> |
|
1128 >>> a = [1, 2, 3, 4, 2, 5, 2] |
|
1129 >>> a.remove(2) |
337 >>> a.remove(2) |
1130 >>> a |
338 >>> a |
1131 [1, 3, 4, 2, 5, 2] |
339 [1, 3, 4, 2, 5, 2]</pre> |
1132 </pre> |
340 </div> |
1133 </div> |
341 <div class="section" title="1.4.8.reverse"> |
1134 <div class="section" title="1.4.8.reverse"> |
342 <div class="titlepage"><div><div><h4 class="title"> |
1135 <div class="titlepage"> |
343 <a name="id2947972"></a>1.4.8.reverse</h4></div></div></div> |
1136 <div> |
344 <p id="ch3list_tuples_20">The <span class="emphasis"><em>reverse</em></span> method reverses elements in the list. It is important to note |
1137 <div> |
345 here that <span class="emphasis"><em>reverse</em></span> method changes the list in-place and doesn't return any |
1138 <h4 class="title"> |
346 thing:</p> |
1139 <a name="id3003405"> |
347 <pre class="programlisting"> |
1140 </a> |
348 >>> a = ['guido', 'alex', 'tim'] |
1141 1.4.8.reverse |
|
1142 </h4> |
|
1143 </div> |
|
1144 </div> |
|
1145 </div> |
|
1146 <p id="ch3list_tuples_20"> |
|
1147 The |
|
1148 <span class="emphasis"> |
|
1149 <em> |
|
1150 reverse |
|
1151 </em> |
|
1152 </span> |
|
1153 method reverses elements in the list. It is important to note |
|
1154 here that |
|
1155 <span class="emphasis"> |
|
1156 <em> |
|
1157 reverse |
|
1158 </em> |
|
1159 </span> |
|
1160 method changes the list in-place and doesn't return any |
|
1161 thing: |
|
1162 </p> |
|
1163 <pre class="programlisting"> |
|
1164 >>> a = ['guido', 'alex', 'tim'] |
|
1165 >>> a.reverse() |
349 >>> a.reverse() |
1166 >>> a |
350 >>> a |
1167 ['tim', 'alex', 'guido'] |
351 ['tim', 'alex', 'guido']</pre> |
1168 </pre> |
352 </div> |
1169 </div> |
353 <div class="section" title="1.4.9.sort"> |
1170 <div class="section" title="1.4.9.sort"> |
354 <div class="titlepage"><div><div><h4 class="title"> |
1171 <div class="titlepage"> |
355 <a name="id2947998"></a>1.4.9.sort</h4></div></div></div> |
1172 <div> |
356 <p id="ch3list_tuples_21">The <span class="emphasis"><em>sort</em></span> method is used to sort the elements of the list. The <span class="emphasis"><em>sort</em></span> method |
1173 <div> |
357 also sorts in-place and does not return anything:</p> |
1174 <h4 class="title"> |
358 <pre class="programlisting"> |
1175 <a name="id3003431"> |
359 >>> a = [5, 1, 3, 7, 4] |
1176 </a> |
|
1177 1.4.9.sort |
|
1178 </h4> |
|
1179 </div> |
|
1180 </div> |
|
1181 </div> |
|
1182 <p id="ch3list_tuples_21"> |
|
1183 The |
|
1184 <span class="emphasis"> |
|
1185 <em> |
|
1186 sort |
|
1187 </em> |
|
1188 </span> |
|
1189 method is used to sort the elements of the list. The |
|
1190 <span class="emphasis"> |
|
1191 <em> |
|
1192 sort |
|
1193 </em> |
|
1194 </span> |
|
1195 method |
|
1196 also sorts in-place and does not return anything: |
|
1197 </p> |
|
1198 <pre class="programlisting"> |
|
1199 >>> a = [5, 1, 3, 7, 4] |
|
1200 >>> a.sort() |
360 >>> a.sort() |
1201 >>> a |
361 >>> a |
1202 [1, 3, 4, 5, 7] |
362 [1, 3, 4, 5, 7]</pre> |
1203 </pre> |
363 <p id="ch3list_tuples_22">In addition to the sort method on a <span class="emphasis"><em>List</em></span> object we can also use the built-in |
1204 <p id="ch3list_tuples_22"> |
364 <span class="strong"><strong>sorted</strong></span> function. This function takes the <span class="emphasis"><em>List</em></span> as a parameter and returns |
1205 In addition to the sort method on a |
365 a sorted copy of the list. However the original list is left intact:</p> |
1206 <span class="emphasis"> |
366 <pre class="programlisting"> |
1207 <em> |
367 >>> a = [5, 1, 3, 7, 4] |
1208 List |
|
1209 </em> |
|
1210 </span> |
|
1211 object we can also use the built-in |
|
1212 <span class="strong"> |
|
1213 <strong> |
|
1214 sorted |
|
1215 </strong> |
|
1216 </span> |
|
1217 function. This function takes the |
|
1218 <span class="emphasis"> |
|
1219 <em> |
|
1220 List |
|
1221 </em> |
|
1222 </span> |
|
1223 as a parameter and returns |
|
1224 a sorted copy of the list. However the original list is left intact: |
|
1225 </p> |
|
1226 <pre class="programlisting"> |
|
1227 >>> a = [5, 1, 3, 7, 4] |
|
1228 >>> b = sorted(a) |
368 >>> b = sorted(a) |
1229 >>> b |
369 >>> b |
1230 [1, 3, 4, 5, 7] |
370 [1, 3, 4, 5, 7] |
1231 >>> a |
371 >>> a |
1232 [5, 1, 3, 7, 4] |
372 [5, 1, 3, 7, 4]</pre> |
1233 </pre> |
373 </div> |
1234 </div> |
374 </div> |
1235 </div> |
375 </div> |
1236 </div> |
376 <div class="section" title="2.Tuples"> |
1237 <div class="section" title="2.Tuples"> |
377 <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
1238 <div class="titlepage"> |
378 <a name="id2948048"></a>2.Tuples</h2></div></div></div> |
1239 <div> |
379 <p id="ch3list_tuples_23"><span class="emphasis"><em>Tuples</em></span> are sequences just like <span class="emphasis"><em>Lists</em></span>, but they are immutable. In other |
1240 <div> |
380 words <span class="emphasis"><em>Tuples</em></span> provides a way to represent a group of items, where the group |
1241 <h2 class="title" style="clear: both"> |
381 of items cannot be changed in any way. The syntax of a <span class="emphasis"><em>Tuple</em></span> is also very |
1242 <a name="id3003481"> |
382 similar to <span class="emphasis"><em>List</em></span>. A <span class="emphasis"><em>Tuple</em></span> is represented with the list of items, called |
1243 </a> |
383 elements of the <span class="emphasis"><em>Tuple</em></span> separated by comma, with the entire list being enclosed |
1244 2.Tuples |
384 in parenthesis. It is not compulsory to use parenthesis around a <span class="emphasis"><em>Tuple</em></span> but |
1245 </h2> |
385 it may be necessary in some of the cases:</p> |
1246 </div> |
386 <pre class="programlisting"> |
1247 </div> |
387 >>> a = 1, 2, 3 |
1248 </div> |
|
1249 <p id="ch3list_tuples_23"> |
|
1250 <span class="emphasis"> |
|
1251 <em> |
|
1252 Tuples |
|
1253 </em> |
|
1254 </span> |
|
1255 are sequences just like |
|
1256 <span class="emphasis"> |
|
1257 <em> |
|
1258 Lists |
|
1259 </em> |
|
1260 </span> |
|
1261 , but they are immutable. In other |
|
1262 words |
|
1263 <span class="emphasis"> |
|
1264 <em> |
|
1265 Tuples |
|
1266 </em> |
|
1267 </span> |
|
1268 provides a way to represent a group of items, where the group |
|
1269 of items cannot be changed in any way. The syntax of a |
|
1270 <span class="emphasis"> |
|
1271 <em> |
|
1272 Tuple |
|
1273 </em> |
|
1274 </span> |
|
1275 is also very |
|
1276 similar to |
|
1277 <span class="emphasis"> |
|
1278 <em> |
|
1279 List |
|
1280 </em> |
|
1281 </span> |
|
1282 . A |
|
1283 <span class="emphasis"> |
|
1284 <em> |
|
1285 Tuple |
|
1286 </em> |
|
1287 </span> |
|
1288 is represented with the list of items, called |
|
1289 elements of the |
|
1290 <span class="emphasis"> |
|
1291 <em> |
|
1292 Tuple |
|
1293 </em> |
|
1294 </span> |
|
1295 separated by comma, with the entire list being enclosed |
|
1296 in parenthesis. It is not compulsory to use parenthesis around a |
|
1297 <span class="emphasis"> |
|
1298 <em> |
|
1299 Tuple |
|
1300 </em> |
|
1301 </span> |
|
1302 but |
|
1303 it may be necessary in some of the cases: |
|
1304 </p> |
|
1305 <pre class="programlisting"> |
|
1306 >>> a = 1, 2, 3 |
|
1307 >>> a |
388 >>> a |
1308 (1, 2, 3) |
389 (1, 2, 3) |
1309 >>> b = 1, |
390 >>> b = 1, |
1310 >>> b |
391 >>> b |
1311 (1,) |
392 (1,)</pre> |
1312 </pre> |
393 <p id="ch3list_tuples_24">It is interesting to note the second example. Just a value followed by a comma |
1313 <p id="ch3list_tuples_24"> |
394 automatically makes that an element of a <span class="emphasis"><em>Tuple</em></span> with only one element. It is |
1314 It is interesting to note the second example. Just a value followed by a comma |
|
1315 automatically makes that an element of a |
|
1316 <span class="emphasis"> |
|
1317 <em> |
|
1318 Tuple |
|
1319 </em> |
|
1320 </span> |
|
1321 with only one element. It is |
|
1322 also important to note that, irrespective of input having a parenthesis, the |
395 also important to note that, irrespective of input having a parenthesis, the |
1323 output always has a parenthesis. |
396 output always has a parenthesis.</p> |
1324 </p> |
397 <p id="ch3list_tuples_25">The first example is also known as <span class="emphasis"><em>Tuple packing</em></span>, because values are being |
1325 <p id="ch3list_tuples_25"> |
398 packed into a tuple. It is also possible to do <span class="emphasis"><em>Tuple unpacking</em></span> which is more |
1326 The first example is also known as |
|
1327 <span class="emphasis"> |
|
1328 <em> |
|
1329 Tuple packing |
|
1330 </em> |
|
1331 </span> |
|
1332 , because values are being |
|
1333 packed into a tuple. It is also possible to do |
|
1334 <span class="emphasis"> |
|
1335 <em> |
|
1336 Tuple unpacking |
|
1337 </em> |
|
1338 </span> |
|
1339 which is more |
|
1340 interesting. It is better to understand that by example. Say we have a |
399 interesting. It is better to understand that by example. Say we have a |
1341 co-ordinate pair from which we need to separate x and y co-ordinates: |
400 co-ordinate pair from which we need to separate x and y co-ordinates:</p> |
1342 </p> |
401 <pre class="programlisting"> |
1343 <pre class="programlisting"> |
402 >>> a = (1, 2) |
1344 >>> a = (1, 2) |
|
1345 >>> x, y = a |
403 >>> x, y = a |
1346 >>> x |
404 >>> x |
1347 1 |
405 1 |
1348 >>> y |
406 >>> y |
1349 2 |
407 2</pre> |
1350 </pre> |
408 <p id="ch3list_tuples_26"><span class="emphasis"><em>Tuple unpacking</em></span> also has several other use-cases of which the most interesting |
1351 <p id="ch3list_tuples_26"> |
|
1352 <span class="emphasis"> |
|
1353 <em> |
|
1354 Tuple unpacking |
|
1355 </em> |
|
1356 </span> |
|
1357 also has several other use-cases of which the most interesting |
|
1358 one is to swap the values of two variables. Using programming languages like C |
409 one is to swap the values of two variables. Using programming languages like C |
1359 would require anywhere around 10 lines of code and an extra temporary variable |
410 would require anywhere around 10 lines of code and an extra temporary variable |
1360 to do this (including all the #include stuff). Python does it in the most |
411 to do this (including all the #include stuff). Python does it in the most |
1361 intuitive way in just one line. Say we want to swap the co-ordinates in the |
412 intuitive way in just one line. Say we want to swap the co-ordinates in the |
1362 above example: |
413 above example:</p> |
1363 </p> |
414 <pre class="programlisting"> |
1364 <pre class="programlisting"> |
415 >>> x, y = y, x |
1365 >>> x, y = y, x |
|
1366 >>> x |
416 >>> x |
1367 2 |
417 2 |
1368 >>> y |
418 >>> y |
1369 1 |
419 1</pre> |
1370 </pre> |
420 <div class="section" title="2.1.Common Tuple Operations"> |
1371 <div class="section" title="2.1.Common Tuple Operations"> |
421 <div class="titlepage"><div><div><h3 class="title"> |
1372 <div class="titlepage"> |
422 <a name="id2948145"></a>2.1.Common Tuple Operations</h3></div></div></div> |
1373 <div> |
423 <p id="ch3list_tuples_27">There is no need to introduce all the <span class="emphasis"><em>Tuple</em></span> operations again, since <span class="emphasis"><em>Tuples</em></span> |
1374 <div> |
424 support the following operations that <span class="emphasis"><em>List</em></span> supports in exactly the same way:</p> |
1375 <h3 class="title"> |
425 <div class="itemizedlist"><ul class="itemizedlist" type="*"> |
1376 <a name="id3003578"> |
426 <li class="listitem" style="list-style-type: *"><p id="ch3list_tuples_28">Indexing</p></li> |
1377 </a> |
427 <li class="listitem" style="list-style-type: *"><p id="ch3list_tuples_29">Concatenating</p></li> |
1378 2.1.Common Tuple Operations |
428 <li class="listitem" style="list-style-type: *"><p id="ch3list_tuples_2a">Slicing</p></li> |
1379 </h3> |
429 <li class="listitem" style="list-style-type: *"><p id="ch3list_tuples_2b">Membership</p></li> |
1380 </div> |
430 <li class="listitem" style="list-style-type: *"><p id="ch3list_tuples_2c">Multiplication</p></li> |
1381 </div> |
431 <li class="listitem" style="list-style-type: *"><p id="ch3list_tuples_2d">Length, Maximum, Minimum</p></li> |
1382 </div> |
432 </ul></div> |
1383 <p id="ch3list_tuples_27"> |
433 <p id="ch3list_tuples_2e">The following examples illustrate the above operations:</p> |
1384 There is no need to introduce all the |
434 <pre class="programlisting"> |
1385 <span class="emphasis"> |
435 >>> a = (1, 2, 3, 4, 5, 6) |
1386 <em> |
|
1387 Tuple |
|
1388 </em> |
|
1389 </span> |
|
1390 operations again, since |
|
1391 <span class="emphasis"> |
|
1392 <em> |
|
1393 Tuples |
|
1394 </em> |
|
1395 </span> |
|
1396 support the following operations that |
|
1397 <span class="emphasis"> |
|
1398 <em> |
|
1399 List |
|
1400 </em> |
|
1401 </span> |
|
1402 supports in exactly the same way: |
|
1403 </p> |
|
1404 <div class="itemizedlist"> |
|
1405 <ul class="itemizedlist" type="*"> |
|
1406 <li class="listitem" style="list-style-type: *"> |
|
1407 <p id="ch3list_tuples_28"> |
|
1408 Indexing |
|
1409 </p> |
|
1410 </li> |
|
1411 <li class="listitem" style="list-style-type: *"> |
|
1412 <p id="ch3list_tuples_29"> |
|
1413 Concatenating |
|
1414 </p> |
|
1415 </li> |
|
1416 <li class="listitem" style="list-style-type: *"> |
|
1417 <p id="ch3list_tuples_2a"> |
|
1418 Slicing |
|
1419 </p> |
|
1420 </li> |
|
1421 <li class="listitem" style="list-style-type: *"> |
|
1422 <p id="ch3list_tuples_2b"> |
|
1423 Membership |
|
1424 </p> |
|
1425 </li> |
|
1426 <li class="listitem" style="list-style-type: *"> |
|
1427 <p id="ch3list_tuples_2c"> |
|
1428 Multiplication |
|
1429 </p> |
|
1430 </li> |
|
1431 <li class="listitem" style="list-style-type: *"> |
|
1432 <p id="ch3list_tuples_2d"> |
|
1433 Length, Maximum, Minimum |
|
1434 </p> |
|
1435 </li> |
|
1436 </ul> |
|
1437 </div> |
|
1438 <p id="ch3list_tuples_2e"> |
|
1439 The following examples illustrate the above operations: |
|
1440 </p> |
|
1441 <pre class="programlisting"> |
|
1442 >>> a = (1, 2, 3, 4, 5, 6) |
|
1443 >>> a[5] |
436 >>> a[5] |
1444 6 |
437 6 |
1445 >>> b = (7, 8, 9) |
438 >>> b = (7, 8, 9) |
1446 >>> a + b |
439 >>> a + b |
1447 (1, 2, 3, 4, 5, 6, 7, 8, 9) |
440 (1, 2, 3, 4, 5, 6, 7, 8, 9) |
1455 >>> len(a) |
448 >>> len(a) |
1456 6 |
449 6 |
1457 >>> max(a) |
450 >>> max(a) |
1458 6 |
451 6 |
1459 >>> min(a) |
452 >>> min(a) |
1460 1 |
453 1</pre> |
1461 </pre> |
454 <p id="ch3list_tuples_2f">However the following <span class="emphasis"><em>List</em></span> operations are not supported by <span class="emphasis"><em>Tuples</em></span> because |
1462 <p id="ch3list_tuples_2f"> |
455 <span class="emphasis"><em>Tuples</em></span> cannot be changed once they are created:</p> |
1463 However the following |
456 <div class="itemizedlist"><ul class="itemizedlist" type="*"> |
1464 <span class="emphasis"> |
457 <li class="listitem" style="list-style-type: *"><p id="ch3list_tuples_30">Changing elements</p></li> |
1465 <em> |
458 <li class="listitem" style="list-style-type: *"><p id="ch3list_tuples_31">Deleting elements</p></li> |
1466 List |
459 <li class="listitem" style="list-style-type: *"><p id="ch3list_tuples_32">Assigning to slices</p></li> |
1467 </em> |
460 </ul></div> |
1468 </span> |
461 <p id="ch3list_tuples_33">Similarity to <span class="emphasis"><em>Lists</em></span> leads to the questions like, why not <span class="emphasis"><em>Lists</em></span> only? Why do |
1469 operations are not supported by |
462 we even want <span class="emphasis"><em>Tuples</em></span>? Can we do the same with <span class="emphasis"><em>Lists</em></span>? And the answer is <span class="strong"><strong>Yes</strong></span> |
1470 <span class="emphasis"> |
463 we can do it, but <span class="emphasis"><em>Tuples</em></span> are helpful at times, like we can return Tuples from |
1471 <em> |
|
1472 Tuples |
|
1473 </em> |
|
1474 </span> |
|
1475 because |
|
1476 <span class="emphasis"> |
|
1477 <em> |
|
1478 Tuples |
|
1479 </em> |
|
1480 </span> |
|
1481 cannot be changed once they are created: |
|
1482 </p> |
|
1483 <div class="itemizedlist"> |
|
1484 <ul class="itemizedlist" type="*"> |
|
1485 <li class="listitem" style="list-style-type: *"> |
|
1486 <p id="ch3list_tuples_30"> |
|
1487 Changing elements |
|
1488 </p> |
|
1489 </li> |
|
1490 <li class="listitem" style="list-style-type: *"> |
|
1491 <p id="ch3list_tuples_31"> |
|
1492 Deleting elements |
|
1493 </p> |
|
1494 </li> |
|
1495 <li class="listitem" style="list-style-type: *"> |
|
1496 <p id="ch3list_tuples_32"> |
|
1497 Assigning to slices |
|
1498 </p> |
|
1499 </li> |
|
1500 </ul> |
|
1501 </div> |
|
1502 <p id="ch3list_tuples_33"> |
|
1503 Similarity to |
|
1504 <span class="emphasis"> |
|
1505 <em> |
|
1506 Lists |
|
1507 </em> |
|
1508 </span> |
|
1509 leads to the questions like, why not |
|
1510 <span class="emphasis"> |
|
1511 <em> |
|
1512 Lists |
|
1513 </em> |
|
1514 </span> |
|
1515 only? Why do |
|
1516 we even want |
|
1517 <span class="emphasis"> |
|
1518 <em> |
|
1519 Tuples |
|
1520 </em> |
|
1521 </span> |
|
1522 ? Can we do the same with |
|
1523 <span class="emphasis"> |
|
1524 <em> |
|
1525 Lists |
|
1526 </em> |
|
1527 </span> |
|
1528 ? And the answer is |
|
1529 <span class="strong"> |
|
1530 <strong> |
|
1531 Yes |
|
1532 </strong> |
|
1533 </span> |
|
1534 we can do it, but |
|
1535 <span class="emphasis"> |
|
1536 <em> |
|
1537 Tuples |
|
1538 </em> |
|
1539 </span> |
|
1540 are helpful at times, like we can return Tuples from |
|
1541 functions. They are also returned by some built-in functions and methods. And |
464 functions. They are also returned by some built-in functions and methods. And |
1542 also there are some use cases like co-ordinate among other things. So |
465 also there are some use cases like co-ordinate among other things. So <span class="emphasis"><em>Tuples</em></span> |
1543 <span class="emphasis"> |
466 are helpful.</p> |
1544 <em> |
467 </div> |
1545 Tuples |
468 </div> |
1546 </em> |
469 <div class="section" title="3.Additional Syntax"> |
1547 </span> |
470 <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
1548 are helpful. |
471 <a name="id2948295"></a>3.Additional Syntax</h2></div></div></div> |
1549 </p> |
472 <p id="ch3list_tuples_34">The following additional syntax are introduced to make it easier to operate on |
1550 </div> |
473 <span class="emphasis"><em>Lists</em></span>.</p> |
1551 </div> |
474 <div class="section" title="3.1.range()"> |
1552 <div class="section" title="3.Additional Syntax"> |
475 <div class="titlepage"><div><div><h3 class="title"> |
1553 <div class="titlepage"> |
476 <a name="id2948312"></a>3.1.range()</h3></div></div></div> |
1554 <div> |
477 <p id="ch3list_tuples_35">The <span class="emphasis"><em>range</em></span> function takes at least one argument and 2 additional optional |
1555 <div> |
|
1556 <h2 class="title" style="clear: both"> |
|
1557 <a name="id3003727"> |
|
1558 </a> |
|
1559 3.Additional Syntax |
|
1560 </h2> |
|
1561 </div> |
|
1562 </div> |
|
1563 </div> |
|
1564 <p id="ch3list_tuples_34"> |
|
1565 The following additional syntax are introduced to make it easier to operate on |
|
1566 <span class="emphasis"> |
|
1567 <em> |
|
1568 Lists |
|
1569 </em> |
|
1570 </span> |
|
1571 . |
|
1572 </p> |
|
1573 <div class="section" title="3.1.range()"> |
|
1574 <div class="titlepage"> |
|
1575 <div> |
|
1576 <div> |
|
1577 <h3 class="title"> |
|
1578 <a name="id3003745"> |
|
1579 </a> |
|
1580 3.1.range() |
|
1581 </h3> |
|
1582 </div> |
|
1583 </div> |
|
1584 </div> |
|
1585 <p id="ch3list_tuples_35"> |
|
1586 The |
|
1587 <span class="emphasis"> |
|
1588 <em> |
|
1589 range |
|
1590 </em> |
|
1591 </span> |
|
1592 function takes at least one argument and 2 additional optional |
|
1593 arguments. If two or more arguments are specified, the range function returns |
478 arguments. If two or more arguments are specified, the range function returns |
1594 a list of natural numbers starting from the first argument passed to it to the |
479 a list of natural numbers starting from the first argument passed to it to the |
1595 second argument. The third argument, if specified is used as a step. Suppose |
480 second argument. The third argument, if specified is used as a step. Suppose |
1596 only one argument is specified, then |
481 only one argument is specified, then <span class="emphasis"><em>range</em></span> function returns a list of natural |
1597 <span class="emphasis"> |
482 numbers starting from 0 upto the argument specified:</p> |
1598 <em> |
483 <pre class="programlisting"> |
1599 range |
484 >>> range(5, 10, 2) |
1600 </em> |
|
1601 </span> |
|
1602 function returns a list of natural |
|
1603 numbers starting from 0 upto the argument specified: |
|
1604 </p> |
|
1605 <pre class="programlisting"> |
|
1606 >>> range(5, 10, 2) |
|
1607 [5, 7, 9] |
485 [5, 7, 9] |
1608 >>> range(2, 15) |
486 >>> range(2, 15) |
1609 [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14] |
487 [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14] |
1610 >>> range(12) |
488 >>> range(12) |
1611 [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11] |
489 [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]</pre> |
1612 </pre> |
490 </div> |
1613 </div> |
491 <div class="section" title="3.2.for"> |
1614 <div class="section" title="3.2.for"> |
492 <div class="titlepage"><div><div><h3 class="title"> |
1615 <div class="titlepage"> |
493 <a name="id2948344"></a>3.2.for</h3></div></div></div> |
1616 <div> |
494 <p id="ch3list_tuples_36">The <span class="strong"><strong>for</strong></span> keyword is used as a part of the looping construct. Unlike for loops |
1617 <div> |
|
1618 <h3 class="title"> |
|
1619 <a name="id3003777"> |
|
1620 </a> |
|
1621 3.2.for |
|
1622 </h3> |
|
1623 </div> |
|
1624 </div> |
|
1625 </div> |
|
1626 <p id="ch3list_tuples_36"> |
|
1627 The |
|
1628 <span class="strong"> |
|
1629 <strong> |
|
1630 for |
|
1631 </strong> |
|
1632 </span> |
|
1633 keyword is used as a part of the looping construct. Unlike for loops |
|
1634 in other languages, Python's for is used to iterate through the elements of |
495 in other languages, Python's for is used to iterate through the elements of |
1635 sequences like |
496 sequences like <span class="emphasis"><em>Lists</em></span>, <span class="emphasis"><em>Tuples</em></span>, <span class="emphasis"><em>Dictionaries</em></span>, etc. The syntax of the for loop |
1636 <span class="emphasis"> |
497 consists of <span class="strong"><strong>for</strong></span>, followed by a variable to hold the individual or the current |
1637 <em> |
498 element of the list during iteration and <span class="strong"><strong>in</strong></span>, followed by the sequence and a |
1638 Lists |
499 semicolon(':') The next line which is part of the <span class="strong"><strong>for</strong></span> loop, i.e the statements |
1639 </em> |
500 that are part of the loop should start with a new intend:</p> |
1640 </span> |
501 <pre class="programlisting"> |
1641 , |
502 >>> names = ['Guido', 'Alex', 'Tim'] |
1642 <span class="emphasis"> |
|
1643 <em> |
|
1644 Tuples |
|
1645 </em> |
|
1646 </span> |
|
1647 , |
|
1648 <span class="emphasis"> |
|
1649 <em> |
|
1650 Dictionaries |
|
1651 </em> |
|
1652 </span> |
|
1653 , etc. The syntax of the for loop |
|
1654 consists of |
|
1655 <span class="strong"> |
|
1656 <strong> |
|
1657 for |
|
1658 </strong> |
|
1659 </span> |
|
1660 , followed by a variable to hold the individual or the current |
|
1661 element of the list during iteration and |
|
1662 <span class="strong"> |
|
1663 <strong> |
|
1664 in |
|
1665 </strong> |
|
1666 </span> |
|
1667 , followed by the sequence and a |
|
1668 semicolon(':') The next line which is part of the |
|
1669 <span class="strong"> |
|
1670 <strong> |
|
1671 for |
|
1672 </strong> |
|
1673 </span> |
|
1674 loop, i.e the statements |
|
1675 that are part of the loop should start with a new intend: |
|
1676 </p> |
|
1677 <pre class="programlisting"> |
|
1678 >>> names = ['Guido', 'Alex', 'Tim'] |
|
1679 >>> for name in names: |
503 >>> for name in names: |
1680 ... print "Name =", name |
504 ... print "Name =", name |
1681 ... |
505 ... |
1682 Name = Guido |
506 Name = Guido |
1683 Name = Alex |
507 Name = Alex |
1684 Name = Tim |
508 Name = Tim</pre> |
1685 </pre> |
509 </div> |
1686 </div> |
510 </div> |
1687 </div> |
511 <div class="section" title="4.Conclusion"> |
1688 <div class="section" title="4.Conclusion"> |
512 <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
1689 <div class="titlepage"> |
513 <a name="id2948403"></a>4.Conclusion</h2></div></div></div> |
1690 <div> |
514 <p id="ch3list_tuples_37">This section on <span class="emphasis"><em>Lists</em></span> and <span class="emphasis"><em>Tuples</em></span> introduces almost all the necessary |
1691 <div> |
515 machinary required to work on <span class="emphasis"><em>Lists</em></span> and <span class="emphasis"><em>Tuples</em></span>. Topics like how to |
1692 <h2 class="title" style="clear: both"> |
|
1693 <a name="id3003836"> |
|
1694 </a> |
|
1695 4.Conclusion |
|
1696 </h2> |
|
1697 </div> |
|
1698 </div> |
|
1699 </div> |
|
1700 <p id="ch3list_tuples_37"> |
|
1701 This section on |
|
1702 <span class="emphasis"> |
|
1703 <em> |
|
1704 Lists |
|
1705 </em> |
|
1706 </span> |
|
1707 and |
|
1708 <span class="emphasis"> |
|
1709 <em> |
|
1710 Tuples |
|
1711 </em> |
|
1712 </span> |
|
1713 introduces almost all the necessary |
|
1714 machinary required to work on |
|
1715 <span class="emphasis"> |
|
1716 <em> |
|
1717 Lists |
|
1718 </em> |
|
1719 </span> |
|
1720 and |
|
1721 <span class="emphasis"> |
|
1722 <em> |
|
1723 Tuples |
|
1724 </em> |
|
1725 </span> |
|
1726 . Topics like how to |
|
1727 use these data structures in bigger more useful programs will be introduced |
516 use these data structures in bigger more useful programs will be introduced |
1728 in the subsequent chapters. |
517 in the subsequent chapters.</p> |
1729 </p> |
518 </div> |
1730 </div> |
519 </div> |
1731 </div> |
520 </div></body> |
1732 </div> |
|
1733 </body> |
|
1734 </html> |
521 </html> |
|
522 |