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| 54 | |
| 55 | <H1><A NAME="SECTION0051000000000000000000"> |
| 56 | 3.10 <tt class="module">operator</tt> -- |
| 57 | Standard operators as functions.</A> |
| 58 | </H1> |
| 59 | <A NAME="module-operator"></A> |
| 60 | |
| 61 | <P> |
| 62 | |
| 63 | <P> |
| 64 | The <tt class="module">operator</tt> module exports a set of functions implemented in C |
| 65 | corresponding to the intrinsic operators of Python. For example, |
| 66 | <code>operator.add(x, y)</code> is equivalent to the expression <code>x+y</code>. The |
| 67 | function names are those used for special class methods; variants without |
| 68 | leading and trailing "<tt class="samp">__</tt>" are also provided for convenience. |
| 69 | |
| 70 | <P> |
| 71 | The functions fall into categories that perform object comparisons, |
| 72 | logical operations, mathematical operations, sequence operations, and |
| 73 | abstract type tests. |
| 74 | |
| 75 | <P> |
| 76 | The object comparison functions are useful for all objects, and are |
| 77 | named after the rich comparison operators they support: |
| 78 | |
| 79 | <P> |
| 80 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 81 | <td><nobr><b><tt id='l2h-490' xml:id='l2h-490' class="function">lt</tt></b>(</nobr></td> |
| 82 | <td><var>a, b</var>)</td></tr></table></dt> |
| 83 | <dd> |
| 84 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 85 | <td><nobr><b><tt class="function">le</tt></b>(</nobr></td> |
| 86 | <td><var>a, b</var>)</td></tr></table></dt> |
| 87 | <dd><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 88 | <td><nobr><b><tt class="function">eq</tt></b>(</nobr></td> |
| 89 | <td><var>a, b</var>)</td></tr></table></dt> |
| 90 | <dd><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 91 | <td><nobr><b><tt class="function">ne</tt></b>(</nobr></td> |
| 92 | <td><var>a, b</var>)</td></tr></table></dt> |
| 93 | <dd><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 94 | <td><nobr><b><tt class="function">ge</tt></b>(</nobr></td> |
| 95 | <td><var>a, b</var>)</td></tr></table></dt> |
| 96 | <dd><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 97 | <td><nobr><b><tt class="function">gt</tt></b>(</nobr></td> |
| 98 | <td><var>a, b</var>)</td></tr></table></dt> |
| 99 | <dd><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 100 | <td><nobr><b><tt class="function">__lt__</tt></b>(</nobr></td> |
| 101 | <td><var>a, b</var>)</td></tr></table></dt> |
| 102 | <dd><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 103 | <td><nobr><b><tt class="function">__le__</tt></b>(</nobr></td> |
| 104 | <td><var>a, b</var>)</td></tr></table></dt> |
| 105 | <dd><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 106 | <td><nobr><b><tt class="function">__eq__</tt></b>(</nobr></td> |
| 107 | <td><var>a, b</var>)</td></tr></table></dt> |
| 108 | <dd><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 109 | <td><nobr><b><tt class="function">__ne__</tt></b>(</nobr></td> |
| 110 | <td><var>a, b</var>)</td></tr></table></dt> |
| 111 | <dd><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 112 | <td><nobr><b><tt class="function">__ge__</tt></b>(</nobr></td> |
| 113 | <td><var>a, b</var>)</td></tr></table></dt> |
| 114 | <dd><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 115 | <td><nobr><b><tt class="function">__gt__</tt></b>(</nobr></td> |
| 116 | <td><var>a, b</var>)</td></tr></table></dt> |
| 117 | <dd>Perform ``rich comparisons'' between <var>a</var> and <var>b</var>. Specifically, |
| 118 | <code>lt(<var>a</var>, <var>b</var>)</code> is equivalent to <code><var>a</var> < <var>b</var></code>, |
| 119 | <code>le(<var>a</var>, <var>b</var>)</code> is equivalent to <code><var>a</var> <= <var>b</var></code>, |
| 120 | <code>eq(<var>a</var>, <var>b</var>)</code> is equivalent to <code><var>a</var> == <var>b</var></code>, |
| 121 | <code>ne(<var>a</var>, <var>b</var>)</code> is equivalent to <code><var>a</var> != <var>b</var></code>, |
| 122 | <code>gt(<var>a</var>, <var>b</var>)</code> is equivalent to <code><var>a</var> > <var>b</var></code> |
| 123 | and |
| 124 | <code>ge(<var>a</var>, <var>b</var>)</code> is equivalent to <code><var>a</var> >= <var>b</var></code>. |
| 125 | Note that unlike the built-in <tt class="function">cmp()</tt>, these functions can |
| 126 | return any value, which may or may not be interpretable as a Boolean |
| 127 | value. See the <em class="citetitle"><a |
| 128 | href="../ref/ref.html" |
| 129 | title="Python Reference Manual" |
| 130 | >Python Reference Manual</a></em> |
| 131 | for more information about rich comparisons. |
| 132 | |
| 133 | <span class="versionnote">New in version 2.2.</span> |
| 134 | |
| 135 | </dl> |
| 136 | |
| 137 | <P> |
| 138 | The logical operations are also generally applicable to all objects, |
| 139 | and support truth tests, identity tests, and boolean operations: |
| 140 | |
| 141 | <P> |
| 142 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 143 | <td><nobr><b><tt id='l2h-502' xml:id='l2h-502' class="function">not_</tt></b>(</nobr></td> |
| 144 | <td><var>o</var>)</td></tr></table></dt> |
| 145 | <dd> |
| 146 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 147 | <td><nobr><b><tt class="function">__not__</tt></b>(</nobr></td> |
| 148 | <td><var>o</var>)</td></tr></table></dt> |
| 149 | <dd>Return the outcome of <tt class="keyword">not</tt> <var>o</var>. (Note that there is no |
| 150 | <tt class="method">__not__()</tt> method for object instances; only the interpreter |
| 151 | core defines this operation. The result is affected by the |
| 152 | <tt class="method">__nonzero__()</tt> and <tt class="method">__len__()</tt> methods.) |
| 153 | </dl> |
| 154 | |
| 155 | <P> |
| 156 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 157 | <td><nobr><b><tt id='l2h-504' xml:id='l2h-504' class="function">truth</tt></b>(</nobr></td> |
| 158 | <td><var>o</var>)</td></tr></table></dt> |
| 159 | <dd> |
| 160 | Return <tt class="constant">True</tt> if <var>o</var> is true, and <tt class="constant">False</tt> |
| 161 | otherwise. This is equivalent to using the <tt class="class">bool</tt> |
| 162 | constructor. |
| 163 | </dl> |
| 164 | |
| 165 | <P> |
| 166 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 167 | <td><nobr><b><tt id='l2h-505' xml:id='l2h-505' class="function">is_</tt></b>(</nobr></td> |
| 168 | <td><var>a, b</var>)</td></tr></table></dt> |
| 169 | <dd> |
| 170 | Return <code><var>a</var> is <var>b</var></code>. Tests object identity. |
| 171 | |
| 172 | <span class="versionnote">New in version 2.3.</span> |
| 173 | |
| 174 | </dl> |
| 175 | |
| 176 | <P> |
| 177 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 178 | <td><nobr><b><tt id='l2h-506' xml:id='l2h-506' class="function">is_not</tt></b>(</nobr></td> |
| 179 | <td><var>a, b</var>)</td></tr></table></dt> |
| 180 | <dd> |
| 181 | Return <code><var>a</var> is not <var>b</var></code>. Tests object identity. |
| 182 | |
| 183 | <span class="versionnote">New in version 2.3.</span> |
| 184 | |
| 185 | </dl> |
| 186 | |
| 187 | <P> |
| 188 | The mathematical and bitwise operations are the most numerous: |
| 189 | |
| 190 | <P> |
| 191 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 192 | <td><nobr><b><tt id='l2h-507' xml:id='l2h-507' class="function">abs</tt></b>(</nobr></td> |
| 193 | <td><var>o</var>)</td></tr></table></dt> |
| 194 | <dd> |
| 195 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 196 | <td><nobr><b><tt class="function">__abs__</tt></b>(</nobr></td> |
| 197 | <td><var>o</var>)</td></tr></table></dt> |
| 198 | <dd>Return the absolute value of <var>o</var>. |
| 199 | </dl> |
| 200 | |
| 201 | <P> |
| 202 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 203 | <td><nobr><b><tt id='l2h-509' xml:id='l2h-509' class="function">add</tt></b>(</nobr></td> |
| 204 | <td><var>a, b</var>)</td></tr></table></dt> |
| 205 | <dd> |
| 206 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 207 | <td><nobr><b><tt class="function">__add__</tt></b>(</nobr></td> |
| 208 | <td><var>a, b</var>)</td></tr></table></dt> |
| 209 | <dd>Return <var>a</var> <code>+</code> <var>b</var>, for <var>a</var> and <var>b</var> numbers. |
| 210 | </dl> |
| 211 | |
| 212 | <P> |
| 213 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 214 | <td><nobr><b><tt id='l2h-511' xml:id='l2h-511' class="function">and_</tt></b>(</nobr></td> |
| 215 | <td><var>a, b</var>)</td></tr></table></dt> |
| 216 | <dd> |
| 217 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 218 | <td><nobr><b><tt class="function">__and__</tt></b>(</nobr></td> |
| 219 | <td><var>a, b</var>)</td></tr></table></dt> |
| 220 | <dd>Return the bitwise and of <var>a</var> and <var>b</var>. |
| 221 | </dl> |
| 222 | |
| 223 | <P> |
| 224 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 225 | <td><nobr><b><tt id='l2h-513' xml:id='l2h-513' class="function">div</tt></b>(</nobr></td> |
| 226 | <td><var>a, b</var>)</td></tr></table></dt> |
| 227 | <dd> |
| 228 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 229 | <td><nobr><b><tt class="function">__div__</tt></b>(</nobr></td> |
| 230 | <td><var>a, b</var>)</td></tr></table></dt> |
| 231 | <dd>Return <var>a</var> <code>/</code> <var>b</var> when <code>__future__.division</code> is not |
| 232 | in effect. This is also known as ``classic'' division. |
| 233 | </dl> |
| 234 | |
| 235 | <P> |
| 236 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 237 | <td><nobr><b><tt id='l2h-515' xml:id='l2h-515' class="function">floordiv</tt></b>(</nobr></td> |
| 238 | <td><var>a, b</var>)</td></tr></table></dt> |
| 239 | <dd> |
| 240 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 241 | <td><nobr><b><tt class="function">__floordiv__</tt></b>(</nobr></td> |
| 242 | <td><var>a, b</var>)</td></tr></table></dt> |
| 243 | <dd>Return <var>a</var> <code>//</code> <var>b</var>. |
| 244 | |
| 245 | <span class="versionnote">New in version 2.2.</span> |
| 246 | |
| 247 | </dl> |
| 248 | |
| 249 | <P> |
| 250 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 251 | <td><nobr><b><tt id='l2h-517' xml:id='l2h-517' class="function">inv</tt></b>(</nobr></td> |
| 252 | <td><var>o</var>)</td></tr></table></dt> |
| 253 | <dd> |
| 254 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 255 | <td><nobr><b><tt class="function">invert</tt></b>(</nobr></td> |
| 256 | <td><var>o</var>)</td></tr></table></dt> |
| 257 | <dd><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 258 | <td><nobr><b><tt class="function">__inv__</tt></b>(</nobr></td> |
| 259 | <td><var>o</var>)</td></tr></table></dt> |
| 260 | <dd><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 261 | <td><nobr><b><tt class="function">__invert__</tt></b>(</nobr></td> |
| 262 | <td><var>o</var>)</td></tr></table></dt> |
| 263 | <dd>Return the bitwise inverse of the number <var>o</var>. This is equivalent |
| 264 | to <code>~</code><var>o</var>. The names <tt class="function">invert()</tt> and |
| 265 | <tt class="function">__invert__()</tt> were added in Python 2.0. |
| 266 | </dl> |
| 267 | |
| 268 | <P> |
| 269 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 270 | <td><nobr><b><tt id='l2h-521' xml:id='l2h-521' class="function">lshift</tt></b>(</nobr></td> |
| 271 | <td><var>a, b</var>)</td></tr></table></dt> |
| 272 | <dd> |
| 273 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 274 | <td><nobr><b><tt class="function">__lshift__</tt></b>(</nobr></td> |
| 275 | <td><var>a, b</var>)</td></tr></table></dt> |
| 276 | <dd>Return <var>a</var> shifted left by <var>b</var>. |
| 277 | </dl> |
| 278 | |
| 279 | <P> |
| 280 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 281 | <td><nobr><b><tt id='l2h-523' xml:id='l2h-523' class="function">mod</tt></b>(</nobr></td> |
| 282 | <td><var>a, b</var>)</td></tr></table></dt> |
| 283 | <dd> |
| 284 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 285 | <td><nobr><b><tt class="function">__mod__</tt></b>(</nobr></td> |
| 286 | <td><var>a, b</var>)</td></tr></table></dt> |
| 287 | <dd>Return <var>a</var> <code>%</code> <var>b</var>. |
| 288 | </dl> |
| 289 | |
| 290 | <P> |
| 291 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 292 | <td><nobr><b><tt id='l2h-525' xml:id='l2h-525' class="function">mul</tt></b>(</nobr></td> |
| 293 | <td><var>a, b</var>)</td></tr></table></dt> |
| 294 | <dd> |
| 295 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 296 | <td><nobr><b><tt class="function">__mul__</tt></b>(</nobr></td> |
| 297 | <td><var>a, b</var>)</td></tr></table></dt> |
| 298 | <dd>Return <var>a</var> <code>*</code> <var>b</var>, for <var>a</var> and <var>b</var> numbers. |
| 299 | </dl> |
| 300 | |
| 301 | <P> |
| 302 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 303 | <td><nobr><b><tt id='l2h-527' xml:id='l2h-527' class="function">neg</tt></b>(</nobr></td> |
| 304 | <td><var>o</var>)</td></tr></table></dt> |
| 305 | <dd> |
| 306 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 307 | <td><nobr><b><tt class="function">__neg__</tt></b>(</nobr></td> |
| 308 | <td><var>o</var>)</td></tr></table></dt> |
| 309 | <dd>Return <var>o</var> negated. |
| 310 | </dl> |
| 311 | |
| 312 | <P> |
| 313 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 314 | <td><nobr><b><tt id='l2h-529' xml:id='l2h-529' class="function">or_</tt></b>(</nobr></td> |
| 315 | <td><var>a, b</var>)</td></tr></table></dt> |
| 316 | <dd> |
| 317 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 318 | <td><nobr><b><tt class="function">__or__</tt></b>(</nobr></td> |
| 319 | <td><var>a, b</var>)</td></tr></table></dt> |
| 320 | <dd>Return the bitwise or of <var>a</var> and <var>b</var>. |
| 321 | </dl> |
| 322 | |
| 323 | <P> |
| 324 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 325 | <td><nobr><b><tt id='l2h-531' xml:id='l2h-531' class="function">pos</tt></b>(</nobr></td> |
| 326 | <td><var>o</var>)</td></tr></table></dt> |
| 327 | <dd> |
| 328 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 329 | <td><nobr><b><tt class="function">__pos__</tt></b>(</nobr></td> |
| 330 | <td><var>o</var>)</td></tr></table></dt> |
| 331 | <dd>Return <var>o</var> positive. |
| 332 | </dl> |
| 333 | |
| 334 | <P> |
| 335 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 336 | <td><nobr><b><tt id='l2h-533' xml:id='l2h-533' class="function">pow</tt></b>(</nobr></td> |
| 337 | <td><var>a, b</var>)</td></tr></table></dt> |
| 338 | <dd> |
| 339 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 340 | <td><nobr><b><tt class="function">__pow__</tt></b>(</nobr></td> |
| 341 | <td><var>a, b</var>)</td></tr></table></dt> |
| 342 | <dd>Return <var>a</var> <code>**</code> <var>b</var>, for <var>a</var> and <var>b</var> numbers. |
| 343 | |
| 344 | <span class="versionnote">New in version 2.3.</span> |
| 345 | |
| 346 | </dl> |
| 347 | |
| 348 | <P> |
| 349 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 350 | <td><nobr><b><tt id='l2h-535' xml:id='l2h-535' class="function">rshift</tt></b>(</nobr></td> |
| 351 | <td><var>a, b</var>)</td></tr></table></dt> |
| 352 | <dd> |
| 353 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 354 | <td><nobr><b><tt class="function">__rshift__</tt></b>(</nobr></td> |
| 355 | <td><var>a, b</var>)</td></tr></table></dt> |
| 356 | <dd>Return <var>a</var> shifted right by <var>b</var>. |
| 357 | </dl> |
| 358 | |
| 359 | <P> |
| 360 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 361 | <td><nobr><b><tt id='l2h-537' xml:id='l2h-537' class="function">sub</tt></b>(</nobr></td> |
| 362 | <td><var>a, b</var>)</td></tr></table></dt> |
| 363 | <dd> |
| 364 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 365 | <td><nobr><b><tt class="function">__sub__</tt></b>(</nobr></td> |
| 366 | <td><var>a, b</var>)</td></tr></table></dt> |
| 367 | <dd>Return <var>a</var> <code>-</code> <var>b</var>. |
| 368 | </dl> |
| 369 | |
| 370 | <P> |
| 371 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 372 | <td><nobr><b><tt id='l2h-539' xml:id='l2h-539' class="function">truediv</tt></b>(</nobr></td> |
| 373 | <td><var>a, b</var>)</td></tr></table></dt> |
| 374 | <dd> |
| 375 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 376 | <td><nobr><b><tt class="function">__truediv__</tt></b>(</nobr></td> |
| 377 | <td><var>a, b</var>)</td></tr></table></dt> |
| 378 | <dd>Return <var>a</var> <code>/</code> <var>b</var> when <code>__future__.division</code> is in |
| 379 | effect. This is also known as division. |
| 380 | |
| 381 | <span class="versionnote">New in version 2.2.</span> |
| 382 | |
| 383 | </dl> |
| 384 | |
| 385 | <P> |
| 386 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 387 | <td><nobr><b><tt id='l2h-541' xml:id='l2h-541' class="function">xor</tt></b>(</nobr></td> |
| 388 | <td><var>a, b</var>)</td></tr></table></dt> |
| 389 | <dd> |
| 390 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 391 | <td><nobr><b><tt class="function">__xor__</tt></b>(</nobr></td> |
| 392 | <td><var>a, b</var>)</td></tr></table></dt> |
| 393 | <dd>Return the bitwise exclusive or of <var>a</var> and <var>b</var>. |
| 394 | </dl> |
| 395 | |
| 396 | <P> |
| 397 | Operations which work with sequences include: |
| 398 | |
| 399 | <P> |
| 400 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 401 | <td><nobr><b><tt id='l2h-543' xml:id='l2h-543' class="function">concat</tt></b>(</nobr></td> |
| 402 | <td><var>a, b</var>)</td></tr></table></dt> |
| 403 | <dd> |
| 404 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 405 | <td><nobr><b><tt class="function">__concat__</tt></b>(</nobr></td> |
| 406 | <td><var>a, b</var>)</td></tr></table></dt> |
| 407 | <dd>Return <var>a</var> <code>+</code> <var>b</var> for <var>a</var> and <var>b</var> sequences. |
| 408 | </dl> |
| 409 | |
| 410 | <P> |
| 411 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 412 | <td><nobr><b><tt id='l2h-545' xml:id='l2h-545' class="function">contains</tt></b>(</nobr></td> |
| 413 | <td><var>a, b</var>)</td></tr></table></dt> |
| 414 | <dd> |
| 415 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 416 | <td><nobr><b><tt class="function">__contains__</tt></b>(</nobr></td> |
| 417 | <td><var>a, b</var>)</td></tr></table></dt> |
| 418 | <dd>Return the outcome of the test <var>b</var> <code>in</code> <var>a</var>. |
| 419 | Note the reversed operands. The name <tt class="function">__contains__()</tt> was |
| 420 | added in Python 2.0. |
| 421 | </dl> |
| 422 | |
| 423 | <P> |
| 424 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 425 | <td><nobr><b><tt id='l2h-547' xml:id='l2h-547' class="function">countOf</tt></b>(</nobr></td> |
| 426 | <td><var>a, b</var>)</td></tr></table></dt> |
| 427 | <dd> |
| 428 | Return the number of occurrences of <var>b</var> in <var>a</var>. |
| 429 | </dl> |
| 430 | |
| 431 | <P> |
| 432 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 433 | <td><nobr><b><tt id='l2h-548' xml:id='l2h-548' class="function">delitem</tt></b>(</nobr></td> |
| 434 | <td><var>a, b</var>)</td></tr></table></dt> |
| 435 | <dd> |
| 436 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 437 | <td><nobr><b><tt class="function">__delitem__</tt></b>(</nobr></td> |
| 438 | <td><var>a, b</var>)</td></tr></table></dt> |
| 439 | <dd>Remove the value of <var>a</var> at index <var>b</var>. |
| 440 | </dl> |
| 441 | |
| 442 | <P> |
| 443 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 444 | <td><nobr><b><tt id='l2h-550' xml:id='l2h-550' class="function">delslice</tt></b>(</nobr></td> |
| 445 | <td><var>a, b, c</var>)</td></tr></table></dt> |
| 446 | <dd> |
| 447 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 448 | <td><nobr><b><tt class="function">__delslice__</tt></b>(</nobr></td> |
| 449 | <td><var>a, b, c</var>)</td></tr></table></dt> |
| 450 | <dd>Delete the slice of <var>a</var> from index <var>b</var> to index <var>c</var><code>-1</code>. |
| 451 | </dl> |
| 452 | |
| 453 | <P> |
| 454 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 455 | <td><nobr><b><tt id='l2h-552' xml:id='l2h-552' class="function">getitem</tt></b>(</nobr></td> |
| 456 | <td><var>a, b</var>)</td></tr></table></dt> |
| 457 | <dd> |
| 458 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 459 | <td><nobr><b><tt class="function">__getitem__</tt></b>(</nobr></td> |
| 460 | <td><var>a, b</var>)</td></tr></table></dt> |
| 461 | <dd>Return the value of <var>a</var> at index <var>b</var>. |
| 462 | </dl> |
| 463 | |
| 464 | <P> |
| 465 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 466 | <td><nobr><b><tt id='l2h-554' xml:id='l2h-554' class="function">getslice</tt></b>(</nobr></td> |
| 467 | <td><var>a, b, c</var>)</td></tr></table></dt> |
| 468 | <dd> |
| 469 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 470 | <td><nobr><b><tt class="function">__getslice__</tt></b>(</nobr></td> |
| 471 | <td><var>a, b, c</var>)</td></tr></table></dt> |
| 472 | <dd>Return the slice of <var>a</var> from index <var>b</var> to index <var>c</var><code>-1</code>. |
| 473 | </dl> |
| 474 | |
| 475 | <P> |
| 476 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 477 | <td><nobr><b><tt id='l2h-556' xml:id='l2h-556' class="function">indexOf</tt></b>(</nobr></td> |
| 478 | <td><var>a, b</var>)</td></tr></table></dt> |
| 479 | <dd> |
| 480 | Return the index of the first of occurrence of <var>b</var> in <var>a</var>. |
| 481 | </dl> |
| 482 | |
| 483 | <P> |
| 484 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 485 | <td><nobr><b><tt id='l2h-557' xml:id='l2h-557' class="function">repeat</tt></b>(</nobr></td> |
| 486 | <td><var>a, b</var>)</td></tr></table></dt> |
| 487 | <dd> |
| 488 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 489 | <td><nobr><b><tt class="function">__repeat__</tt></b>(</nobr></td> |
| 490 | <td><var>a, b</var>)</td></tr></table></dt> |
| 491 | <dd>Return <var>a</var> <code>*</code> <var>b</var> where <var>a</var> is a sequence and |
| 492 | <var>b</var> is an integer. |
| 493 | </dl> |
| 494 | |
| 495 | <P> |
| 496 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 497 | <td><nobr><b><tt id='l2h-559' xml:id='l2h-559' class="function">sequenceIncludes</tt></b>(</nobr></td> |
| 498 | <td><var>...</var>)</td></tr></table></dt> |
| 499 | <dd> |
| 500 | <div class="versionnote"><b>Deprecated since release 2.0.</b> |
| 501 | Use <tt class="function">contains()</tt> instead.</div><p></p> |
| 502 | Alias for <tt class="function">contains()</tt>. |
| 503 | </dl> |
| 504 | |
| 505 | <P> |
| 506 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 507 | <td><nobr><b><tt id='l2h-560' xml:id='l2h-560' class="function">setitem</tt></b>(</nobr></td> |
| 508 | <td><var>a, b, c</var>)</td></tr></table></dt> |
| 509 | <dd> |
| 510 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 511 | <td><nobr><b><tt class="function">__setitem__</tt></b>(</nobr></td> |
| 512 | <td><var>a, b, c</var>)</td></tr></table></dt> |
| 513 | <dd>Set the value of <var>a</var> at index <var>b</var> to <var>c</var>. |
| 514 | </dl> |
| 515 | |
| 516 | <P> |
| 517 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 518 | <td><nobr><b><tt id='l2h-562' xml:id='l2h-562' class="function">setslice</tt></b>(</nobr></td> |
| 519 | <td><var>a, b, c, v</var>)</td></tr></table></dt> |
| 520 | <dd> |
| 521 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 522 | <td><nobr><b><tt class="function">__setslice__</tt></b>(</nobr></td> |
| 523 | <td><var>a, b, c, v</var>)</td></tr></table></dt> |
| 524 | <dd>Set the slice of <var>a</var> from index <var>b</var> to index <var>c</var><code>-1</code> to the |
| 525 | sequence <var>v</var>. |
| 526 | </dl> |
| 527 | |
| 528 | <P> |
| 529 | The <tt class="module">operator</tt> module also defines a few predicates to test the |
| 530 | type of objects. <span class="note"><b class="label">Note:</b> |
| 531 | Be careful not to misinterpret the |
| 532 | results of these functions; only <tt class="function">isCallable()</tt> has any |
| 533 | measure of reliability with instance objects. For example:</span> |
| 534 | |
| 535 | <P> |
| 536 | <div class="verbatim"><pre> |
| 537 | >>> class C: |
| 538 | ... pass |
| 539 | ... |
| 540 | >>> import operator |
| 541 | >>> o = C() |
| 542 | >>> operator.isMappingType(o) |
| 543 | True |
| 544 | </pre></div> |
| 545 | |
| 546 | <P> |
| 547 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 548 | <td><nobr><b><tt id='l2h-564' xml:id='l2h-564' class="function">isCallable</tt></b>(</nobr></td> |
| 549 | <td><var>o</var>)</td></tr></table></dt> |
| 550 | <dd> |
| 551 | <div class="versionnote"><b>Deprecated since release 2.0.</b> |
| 552 | Use the <tt class="function">callable()</tt> built-in function instead.</div><p></p> |
| 553 | Returns true if the object <var>o</var> can be called like a function, |
| 554 | otherwise it returns false. True is returned for functions, bound and |
| 555 | unbound methods, class objects, and instance objects which support the |
| 556 | <tt class="method">__call__()</tt> method. |
| 557 | </dl> |
| 558 | |
| 559 | <P> |
| 560 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 561 | <td><nobr><b><tt id='l2h-565' xml:id='l2h-565' class="function">isMappingType</tt></b>(</nobr></td> |
| 562 | <td><var>o</var>)</td></tr></table></dt> |
| 563 | <dd> |
| 564 | Returns true if the object <var>o</var> supports the mapping interface. |
| 565 | This is true for dictionaries and all instance objects defining |
| 566 | <tt class="method">__getitem__</tt>. |
| 567 | <span class="warning"><b class="label">Warning:</b> |
| 568 | There is no reliable way to test if an instance |
| 569 | supports the complete mapping protocol since the interface itself is |
| 570 | ill-defined. This makes this test less useful than it otherwise might |
| 571 | be.</span> |
| 572 | </dl> |
| 573 | |
| 574 | <P> |
| 575 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 576 | <td><nobr><b><tt id='l2h-566' xml:id='l2h-566' class="function">isNumberType</tt></b>(</nobr></td> |
| 577 | <td><var>o</var>)</td></tr></table></dt> |
| 578 | <dd> |
| 579 | Returns true if the object <var>o</var> represents a number. This is true |
| 580 | for all numeric types implemented in C. |
| 581 | <span class="warning"><b class="label">Warning:</b> |
| 582 | There is no reliable way to test if an instance |
| 583 | supports the complete numeric interface since the interface itself is |
| 584 | ill-defined. This makes this test less useful than it otherwise might |
| 585 | be.</span> |
| 586 | </dl> |
| 587 | |
| 588 | <P> |
| 589 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 590 | <td><nobr><b><tt id='l2h-567' xml:id='l2h-567' class="function">isSequenceType</tt></b>(</nobr></td> |
| 591 | <td><var>o</var>)</td></tr></table></dt> |
| 592 | <dd> |
| 593 | Returns true if the object <var>o</var> supports the sequence protocol. |
| 594 | This returns true for all objects which define sequence methods in C, |
| 595 | and for all instance objects defining <tt class="method">__getitem__</tt>. |
| 596 | <span class="warning"><b class="label">Warning:</b> |
| 597 | There is no reliable |
| 598 | way to test if an instance supports the complete sequence interface |
| 599 | since the interface itself is ill-defined. This makes this test less |
| 600 | useful than it otherwise might be.</span> |
| 601 | </dl> |
| 602 | |
| 603 | <P> |
| 604 | Example: Build a dictionary that maps the ordinals from <code>0</code> to |
| 605 | <code>255</code> to their character equivalents. |
| 606 | |
| 607 | <P> |
| 608 | <div class="verbatim"><pre> |
| 609 | >>> import operator |
| 610 | >>> d = {} |
| 611 | >>> keys = range(256) |
| 612 | >>> vals = map(chr, keys) |
| 613 | >>> map(operator.setitem, [d]*len(keys), keys, vals) |
| 614 | </pre></div> |
| 615 | |
| 616 | <P> |
| 617 | The <tt class="module">operator</tt> module also defines tools for generalized attribute |
| 618 | and item lookups. These are useful for making fast field extractors |
| 619 | as arguments for <tt class="function">map()</tt>, <tt class="function">sorted()</tt>, |
| 620 | <tt class="method">itertools.groupby()</tt>, or other functions that expect a |
| 621 | function argument. |
| 622 | |
| 623 | <P> |
| 624 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 625 | <td><nobr><b><tt id='l2h-568' xml:id='l2h-568' class="function">attrgetter</tt></b>(</nobr></td> |
| 626 | <td><var>attr</var>)</td></tr></table></dt> |
| 627 | <dd> |
| 628 | Return a callable object that fetches <var>attr</var> from its operand. |
| 629 | After, "<tt class="samp">f=attrgetter('name')</tt>", the call "<tt class="samp">f(b)</tt>" returns |
| 630 | "<tt class="samp">b.name</tt>". |
| 631 | |
| 632 | <span class="versionnote">New in version 2.4.</span> |
| 633 | |
| 634 | </dl> |
| 635 | |
| 636 | <P> |
| 637 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 638 | <td><nobr><b><tt id='l2h-569' xml:id='l2h-569' class="function">itemgetter</tt></b>(</nobr></td> |
| 639 | <td><var>item</var>)</td></tr></table></dt> |
| 640 | <dd> |
| 641 | Return a callable object that fetches <var>item</var> from its operand. |
| 642 | After, "<tt class="samp">f=itemgetter(2)</tt>", the call "<tt class="samp">f(b)</tt>" returns |
| 643 | "<tt class="samp">b[2]</tt>". |
| 644 | |
| 645 | <span class="versionnote">New in version 2.4.</span> |
| 646 | |
| 647 | </dl> |
| 648 | |
| 649 | <P> |
| 650 | Examples: |
| 651 | |
| 652 | <P> |
| 653 | <div class="verbatim"><pre> |
| 654 | >>> from operator import * |
| 655 | >>> inventory = [('apple', 3), ('banana', 2), ('pear', 5), ('orange', 1)] |
| 656 | >>> getcount = itemgetter(1) |
| 657 | >>> map(getcount, inventory) |
| 658 | [3, 2, 5, 1] |
| 659 | >>> sorted(inventory, key=getcount) |
| 660 | [('orange', 1), ('banana', 2), ('apple', 3), ('pear', 5)] |
| 661 | </pre></div> |
| 662 | |
| 663 | <P> |
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