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| 55 | <H1><A NAME="SECTION009500000000000000000"> |
| 56 | 7.5 <tt class="module">threading</tt> -- |
| 57 | Higher-level threading interface</A> |
| 58 | </H1> |
| 59 | |
| 60 | <P> |
| 61 | <A NAME="module-threading"></A> |
| 62 | |
| 63 | <P> |
| 64 | This module constructs higher-level threading interfaces on top of the |
| 65 | lower level <tt class="module"><a href="module-thread.html">thread</a></tt> module. |
| 66 | |
| 67 | <P> |
| 68 | The <tt class="module"><a href="module-dummythreading.html">dummy_threading</a></tt> module is provided for |
| 69 | situations where <tt class="module">threading</tt> cannot be used because |
| 70 | <tt class="module"><a href="module-thread.html">thread</a></tt> is missing. |
| 71 | |
| 72 | <P> |
| 73 | This module defines the following functions and objects: |
| 74 | |
| 75 | <P> |
| 76 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 77 | <td><nobr><b><tt id='l2h-2704' xml:id='l2h-2704' class="function">activeCount</tt></b>(</nobr></td> |
| 78 | <td><var></var>)</td></tr></table></dt> |
| 79 | <dd> |
| 80 | Return the number of currently active <tt class="class">Thread</tt> objects. |
| 81 | The returned count is equal to the length of the list returned by |
| 82 | <tt class="function">enumerate()</tt>. |
| 83 | A function that returns the number of currently active threads. |
| 84 | </dl> |
| 85 | |
| 86 | <P> |
| 87 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 88 | <td><nobr><b><tt id='l2h-2705' xml:id='l2h-2705' class="function">Condition</tt></b>(</nobr></td> |
| 89 | <td><var></var>)</td></tr></table></dt> |
| 90 | <dd> |
| 91 | A factory function that returns a new condition variable object. |
| 92 | A condition variable allows one or more threads to wait until they |
| 93 | are notified by another thread. |
| 94 | </dl> |
| 95 | |
| 96 | <P> |
| 97 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 98 | <td><nobr><b><tt id='l2h-2706' xml:id='l2h-2706' class="function">currentThread</tt></b>(</nobr></td> |
| 99 | <td><var></var>)</td></tr></table></dt> |
| 100 | <dd> |
| 101 | Return the current <tt class="class">Thread</tt> object, corresponding to the |
| 102 | caller's thread of control. If the caller's thread of control was not |
| 103 | created through the |
| 104 | <tt class="module">threading</tt> module, a dummy thread object with limited functionality |
| 105 | is returned. |
| 106 | </dl> |
| 107 | |
| 108 | <P> |
| 109 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 110 | <td><nobr><b><tt id='l2h-2707' xml:id='l2h-2707' class="function">enumerate</tt></b>(</nobr></td> |
| 111 | <td><var></var>)</td></tr></table></dt> |
| 112 | <dd> |
| 113 | Return a list of all currently active <tt class="class">Thread</tt> objects. |
| 114 | The list includes daemonic threads, dummy thread objects created |
| 115 | by <tt class="function">currentThread()</tt>, and the main thread. It excludes terminated |
| 116 | threads and threads that have not yet been started. |
| 117 | </dl> |
| 118 | |
| 119 | <P> |
| 120 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 121 | <td><nobr><b><tt id='l2h-2708' xml:id='l2h-2708' class="function">Event</tt></b>(</nobr></td> |
| 122 | <td><var></var>)</td></tr></table></dt> |
| 123 | <dd> |
| 124 | A factory function that returns a new event object. An event manages |
| 125 | a flag that can be set to true with the <tt class="method">set()</tt> method and |
| 126 | reset to false with the <tt class="method">clear()</tt> method. The <tt class="method">wait()</tt> |
| 127 | method blocks until the flag is true. |
| 128 | </dl> |
| 129 | |
| 130 | <P> |
| 131 | <dl><dt><b><span class="typelabel">class</span> <tt id='l2h-2709' xml:id='l2h-2709' class="class">local</tt></b> |
| 132 | <dd> |
| 133 | A class that represents thread-local data. Thread-local data are data |
| 134 | whose values are thread specific. To manage thread-local data, just |
| 135 | create an instance of <tt class="class">local</tt> (or a subclass) and store |
| 136 | attributes on it: |
| 137 | |
| 138 | <P> |
| 139 | <div class="verbatim"><pre> |
| 140 | mydata = threading.local() |
| 141 | mydata.x = 1 |
| 142 | </pre></div> |
| 143 | |
| 144 | <P> |
| 145 | The instance's values will be different for separate threads. |
| 146 | |
| 147 | <P> |
| 148 | For more details and extensive examples, see the documentation string |
| 149 | of the <tt class="module">_threading_local</tt> module. |
| 150 | |
| 151 | <P> |
| 152 | |
| 153 | <span class="versionnote">New in version 2.4.</span> |
| 154 | |
| 155 | </dl> |
| 156 | |
| 157 | <P> |
| 158 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 159 | <td><nobr><b><tt id='l2h-2710' xml:id='l2h-2710' class="function">Lock</tt></b>(</nobr></td> |
| 160 | <td><var></var>)</td></tr></table></dt> |
| 161 | <dd> |
| 162 | A factory function that returns a new primitive lock object. Once |
| 163 | a thread has acquired it, subsequent attempts to acquire it block, |
| 164 | until it is released; any thread may release it. |
| 165 | </dl> |
| 166 | |
| 167 | <P> |
| 168 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 169 | <td><nobr><b><tt id='l2h-2711' xml:id='l2h-2711' class="function">RLock</tt></b>(</nobr></td> |
| 170 | <td><var></var>)</td></tr></table></dt> |
| 171 | <dd> |
| 172 | A factory function that returns a new reentrant lock object. |
| 173 | A reentrant lock must be released by the thread that acquired it. |
| 174 | Once a thread has acquired a reentrant lock, the same thread may |
| 175 | acquire it again without blocking; the thread must release it once |
| 176 | for each time it has acquired it. |
| 177 | </dl> |
| 178 | |
| 179 | <P> |
| 180 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 181 | <td><nobr><b><tt id='l2h-2712' xml:id='l2h-2712' class="function">Semaphore</tt></b>(</nobr></td> |
| 182 | <td><var></var><big>[</big><var>value</var><big>]</big><var></var>)</td></tr></table></dt> |
| 183 | <dd> |
| 184 | A factory function that returns a new semaphore object. A |
| 185 | semaphore manages a counter representing the number of <tt class="method">release()</tt> |
| 186 | calls minus the number of <tt class="method">acquire()</tt> calls, plus an initial value. |
| 187 | The <tt class="method">acquire()</tt> method blocks if necessary until it can return |
| 188 | without making the counter negative. If not given, <var>value</var> defaults to |
| 189 | 1. |
| 190 | </dl> |
| 191 | |
| 192 | <P> |
| 193 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 194 | <td><nobr><b><tt id='l2h-2713' xml:id='l2h-2713' class="function">BoundedSemaphore</tt></b>(</nobr></td> |
| 195 | <td><var></var><big>[</big><var>value</var><big>]</big><var></var>)</td></tr></table></dt> |
| 196 | <dd> |
| 197 | A factory function that returns a new bounded semaphore object. A bounded |
| 198 | semaphore checks to make sure its current value doesn't exceed its initial |
| 199 | value. If it does, <tt class="exception">ValueError</tt> is raised. In most situations |
| 200 | semaphores are used to guard resources with limited capacity. If the |
| 201 | semaphore is released too many times it's a sign of a bug. If not given, |
| 202 | <var>value</var> defaults to 1. |
| 203 | </dl> |
| 204 | |
| 205 | <P> |
| 206 | <dl><dt><b><span class="typelabel">class</span> <tt id='l2h-2714' xml:id='l2h-2714' class="class">Thread</tt></b> |
| 207 | <dd> |
| 208 | A class that represents a thread of control. This class can be safely |
| 209 | subclassed in a limited fashion. |
| 210 | </dl> |
| 211 | |
| 212 | <P> |
| 213 | <dl><dt><b><span class="typelabel">class</span> <tt id='l2h-2715' xml:id='l2h-2715' class="class">Timer</tt></b> |
| 214 | <dd> |
| 215 | A thread that executes a function after a specified interval has passed. |
| 216 | </dl> |
| 217 | |
| 218 | <P> |
| 219 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 220 | <td><nobr><b><tt id='l2h-2716' xml:id='l2h-2716' class="function">settrace</tt></b>(</nobr></td> |
| 221 | <td><var>func</var>)</td></tr></table></dt> |
| 222 | <dd> |
| 223 | Set a trace function<a id='l2h-2718' xml:id='l2h-2718'></a> for all threads started |
| 224 | from the <tt class="module">threading</tt> module. The <var>func</var> will be passed to |
| 225 | <tt class="function">sys.settrace()</tt> for each thread, before its <tt class="method">run()</tt> |
| 226 | method is called. |
| 227 | |
| 228 | <span class="versionnote">New in version 2.3.</span> |
| 229 | |
| 230 | </dl> |
| 231 | |
| 232 | <P> |
| 233 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 234 | <td><nobr><b><tt id='l2h-2717' xml:id='l2h-2717' class="function">setprofile</tt></b>(</nobr></td> |
| 235 | <td><var>func</var>)</td></tr></table></dt> |
| 236 | <dd> |
| 237 | Set a profile function<a id='l2h-2719' xml:id='l2h-2719'></a> for all threads started |
| 238 | from the <tt class="module">threading</tt> module. The <var>func</var> will be passed to |
| 239 | <tt class="function">sys.setprofile()</tt> for each thread, before its <tt class="method">run()</tt> |
| 240 | method is called. |
| 241 | |
| 242 | <span class="versionnote">New in version 2.3.</span> |
| 243 | |
| 244 | </dl> |
| 245 | |
| 246 | <P> |
| 247 | Detailed interfaces for the objects are documented below. |
| 248 | |
| 249 | <P> |
| 250 | The design of this module is loosely based on Java's threading model. |
| 251 | However, where Java makes locks and condition variables basic behavior |
| 252 | of every object, they are separate objects in Python. Python's <tt class="class">Thread</tt> |
| 253 | class supports a subset of the behavior of Java's Thread class; |
| 254 | currently, there are no priorities, no thread groups, and threads |
| 255 | cannot be destroyed, stopped, suspended, resumed, or interrupted. The |
| 256 | static methods of Java's Thread class, when implemented, are mapped to |
| 257 | module-level functions. |
| 258 | |
| 259 | <P> |
| 260 | All of the methods described below are executed atomically. |
| 261 | |
| 262 | <P> |
| 263 | |
| 264 | <p><br /></p><hr class='online-navigation' /> |
| 265 | <div class='online-navigation'> |
| 266 | <!--Table of Child-Links--> |
| 267 | <A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></a> |
| 268 | |
| 269 | <UL CLASS="ChildLinks"> |
| 270 | <LI><A href="lock-objects.html">7.5.1 Lock Objects</a> |
| 271 | <LI><A href="rlock-objects.html">7.5.2 RLock Objects</a> |
| 272 | <LI><A href="condition-objects.html">7.5.3 Condition Objects</a> |
| 273 | <LI><A href="semaphore-objects.html">7.5.4 Semaphore Objects</a> |
| 274 | <UL> |
| 275 | <LI><A href="semaphore-examples.html">7.5.4.1 <tt class="class">Semaphore</tt> Example</a> |
| 276 | </ul> |
| 277 | <LI><A href="event-objects.html">7.5.5 Event Objects</a> |
| 278 | <LI><A href="thread-objects.html">7.5.6 Thread Objects</a> |
| 279 | <LI><A href="timer-objects.html">7.5.7 Timer Objects</a> |
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