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<li><a class="reference internal" href="#">队列集</a><ul>
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<li><a class="reference internal" href="#queue">Queue</a></li>
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<li><a class="reference internal" href="#priority-queue">优先级队列</a></li>
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<section id="queues">
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<span id="asyncio-queues"></span><h1>队列集<a class="headerlink" href="#queues" title="永久链接至标题">¶</a></h1>
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<p><strong>源代码:</strong> <a class="reference external" href="https://github.com/python/cpython/tree/3.8/Lib/asyncio/queues.py">Lib/asyncio/queues.py</a></p>
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<p>asyncio 队列被设计成与 <a class="reference internal" href="queue.html#module-queue" title="queue: A synchronized queue class."><code class="xref py py-mod docutils literal notranslate"><span class="pre">queue</span></code></a> 模块类似。尽管 asyncio队列不是线程安全的，但是他们是被设计专用于 async/await 代码。</p>
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<p>注意asyncio 的队列没有 <em>timeout</em> 形参；请使用 <a class="reference internal" href="asyncio-task.html#asyncio.wait_for" title="asyncio.wait_for"><code class="xref py py-func docutils literal notranslate"><span class="pre">asyncio.wait_for()</span></code></a> 函数为队列添加超时操作。</p>
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<p>参见下面的 <a class="reference internal" href="#examples">Examples</a> 部分。</p>
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<section id="queue">
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<h2>Queue<a class="headerlink" href="#queue" title="永久链接至标题">¶</a></h2>
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<dl class="class">
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<dt id="asyncio.Queue">
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<em class="property">class </em><code class="sig-prename descclassname">asyncio.</code><code class="sig-name descname">Queue</code><span class="sig-paren">(</span><em class="sig-param">maxsize=0</em>, <em class="sig-param">*</em>, <em class="sig-param">loop=None</em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Queue" title="永久链接至目标">¶</a></dt>
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<dd><p>先进，先出（FIFO）队列</p>
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<p>如果 <em>maxsize</em> 小于等于零，则队列尺寸是无限的。如果是大于 <code class="docutils literal notranslate"><span class="pre">0</span></code> 的整数，则当队列达到 <em>maxsize</em> 时， <code class="docutils literal notranslate"><span class="pre">await</span> <span class="pre">put()</span></code> 将阻塞至某个元素被 <a class="reference internal" href="#asyncio.Queue.get" title="asyncio.Queue.get"><code class="xref py py-meth docutils literal notranslate"><span class="pre">get()</span></code></a> 取出。</p>
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<p>不像标准库中的并发型 <a class="reference internal" href="queue.html#module-queue" title="queue: A synchronized queue class."><code class="xref py py-mod docutils literal notranslate"><span class="pre">queue</span></code></a> ，队列的尺寸一直是已知的，可以通过调用 <a class="reference internal" href="#asyncio.Queue.qsize" title="asyncio.Queue.qsize"><code class="xref py py-meth docutils literal notranslate"><span class="pre">qsize()</span></code></a> 方法返回。</p>
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<div class="deprecated-removed">
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<p><span class="versionmodified">Deprecated since version 3.8, will be removed in version 3.10: </span><em>loop</em> 形参。</p>
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</div>
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<p>这个类不是线程安全的（<a class="reference internal" href="asyncio-dev.html#asyncio-multithreading"><span class="std std-ref">not thread safe</span></a>）。</p>
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<dl class="attribute">
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||
<dt id="asyncio.Queue.maxsize">
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<code class="sig-name descname">maxsize</code><a class="headerlink" href="#asyncio.Queue.maxsize" title="永久链接至目标">¶</a></dt>
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<dd><p>队列中可存放的元素数量。</p>
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</dd></dl>
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<dl class="method">
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<dt id="asyncio.Queue.empty">
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<code class="sig-name descname">empty</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Queue.empty" title="永久链接至目标">¶</a></dt>
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<dd><p>如果队列为空返回 <code class="docutils literal notranslate"><span class="pre">True</span></code> ，否则返回 <code class="docutils literal notranslate"><span class="pre">False</span></code> 。</p>
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</dd></dl>
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<dl class="method">
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<dt id="asyncio.Queue.full">
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<code class="sig-name descname">full</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Queue.full" title="永久链接至目标">¶</a></dt>
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<dd><p>如果有 <a class="reference internal" href="#asyncio.Queue.maxsize" title="asyncio.Queue.maxsize"><code class="xref py py-attr docutils literal notranslate"><span class="pre">maxsize</span></code></a> 个条目在队列中，则返回 <code class="docutils literal notranslate"><span class="pre">True</span></code> 。</p>
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<p>如果队列用 <code class="docutils literal notranslate"><span class="pre">maxsize=0</span></code> （默认）初始化，则 <a class="reference internal" href="#asyncio.Queue.full" title="asyncio.Queue.full"><code class="xref py py-meth docutils literal notranslate"><span class="pre">full()</span></code></a> 永远不会返回 <code class="docutils literal notranslate"><span class="pre">True</span></code> 。</p>
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</dd></dl>
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<dl class="method">
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<dt id="asyncio.Queue.get">
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<em class="property">coroutine </em><code class="sig-name descname">get</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Queue.get" title="永久链接至目标">¶</a></dt>
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<dd><p>从队列中删除并返回一个元素。如果队列为空，则等待，直到队列中有元素。</p>
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</dd></dl>
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<dl class="method">
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<dt id="asyncio.Queue.get_nowait">
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<code class="sig-name descname">get_nowait</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Queue.get_nowait" title="永久链接至目标">¶</a></dt>
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<dd><p>立即返回一个队列中的元素，如果队列内有值，否则引发异常 <a class="reference internal" href="#asyncio.QueueEmpty" title="asyncio.QueueEmpty"><code class="xref py py-exc docutils literal notranslate"><span class="pre">QueueEmpty</span></code></a> 。</p>
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</dd></dl>
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<dl class="method">
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<dt id="asyncio.Queue.join">
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<em class="property">coroutine </em><code class="sig-name descname">join</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Queue.join" title="永久链接至目标">¶</a></dt>
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<dd><p>阻塞至队列中所有的元素都被接收和处理完毕。</p>
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<p>当条目添加到队列的时候，未完成任务的计数就会增加。每当消费协程调用 <a class="reference internal" href="#asyncio.Queue.task_done" title="asyncio.Queue.task_done"><code class="xref py py-meth docutils literal notranslate"><span class="pre">task_done()</span></code></a> 表示这个条目已经被回收，该条目所有工作已经完成，未完成计数就会减少。当未完成计数降到零的时候， <a class="reference internal" href="#asyncio.Queue.join" title="asyncio.Queue.join"><code class="xref py py-meth docutils literal notranslate"><span class="pre">join()</span></code></a> 阻塞被解除。</p>
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</dd></dl>
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<dl class="method">
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<dt id="asyncio.Queue.put">
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<em class="property">coroutine </em><code class="sig-name descname">put</code><span class="sig-paren">(</span><em class="sig-param">item</em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Queue.put" title="永久链接至目标">¶</a></dt>
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<dd><p>添加一个元素进队列。如果队列满了，在添加元素之前，会一直等待空闲插槽可用。</p>
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</dd></dl>
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<dl class="method">
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<dt id="asyncio.Queue.put_nowait">
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<code class="sig-name descname">put_nowait</code><span class="sig-paren">(</span><em class="sig-param">item</em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Queue.put_nowait" title="永久链接至目标">¶</a></dt>
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<dd><p>不阻塞的放一个元素入队列。</p>
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<p>如果没有立即可用的空闲槽，引发 <a class="reference internal" href="#asyncio.QueueFull" title="asyncio.QueueFull"><code class="xref py py-exc docutils literal notranslate"><span class="pre">QueueFull</span></code></a> 异常。</p>
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||
</dd></dl>
|
||
|
||
<dl class="method">
|
||
<dt id="asyncio.Queue.qsize">
|
||
<code class="sig-name descname">qsize</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Queue.qsize" title="永久链接至目标">¶</a></dt>
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<dd><p>返回队列用的元素数量。</p>
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</dd></dl>
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|
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<dl class="method">
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<dt id="asyncio.Queue.task_done">
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||
<code class="sig-name descname">task_done</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Queue.task_done" title="永久链接至目标">¶</a></dt>
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||
<dd><p>表明前面排队的任务已经完成，即get出来的元素相关操作已经完成。</p>
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<p>由队列使用者控制。每个 <a class="reference internal" href="#asyncio.Queue.get" title="asyncio.Queue.get"><code class="xref py py-meth docutils literal notranslate"><span class="pre">get()</span></code></a> 用于获取一个任务，任务最后调用 <a class="reference internal" href="#asyncio.Queue.task_done" title="asyncio.Queue.task_done"><code class="xref py py-meth docutils literal notranslate"><span class="pre">task_done()</span></code></a> 告诉队列，这个任务已经完成。</p>
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||
<p>如果 <a class="reference internal" href="#asyncio.Queue.join" title="asyncio.Queue.join"><code class="xref py py-meth docutils literal notranslate"><span class="pre">join()</span></code></a> 当前正在阻塞，在所有条目都被处理后，将解除阻塞(意味着每个 <a class="reference internal" href="#asyncio.Queue.put" title="asyncio.Queue.put"><code class="xref py py-meth docutils literal notranslate"><span class="pre">put()</span></code></a> 进队列的条目的 <a class="reference internal" href="#asyncio.Queue.task_done" title="asyncio.Queue.task_done"><code class="xref py py-meth docutils literal notranslate"><span class="pre">task_done()</span></code></a> 都被收到)。</p>
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<p>如果被调用的次数多于放入队列中的项目数量，将引发 <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a> 。</p>
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</dd></dl>
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</dd></dl>
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</section>
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<section id="priority-queue">
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<h2>优先级队列<a class="headerlink" href="#priority-queue" title="永久链接至标题">¶</a></h2>
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<dl class="class">
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<dt id="asyncio.PriorityQueue">
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||
<em class="property">class </em><code class="sig-prename descclassname">asyncio.</code><code class="sig-name descname">PriorityQueue</code><a class="headerlink" href="#asyncio.PriorityQueue" title="永久链接至目标">¶</a></dt>
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||
<dd><p><a class="reference internal" href="#asyncio.Queue" title="asyncio.Queue"><code class="xref py py-class docutils literal notranslate"><span class="pre">Queue</span></code></a> 的变体；按优先级顺序取出条目 (最小的先取出)。</p>
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||
<p>条目通常是 <code class="docutils literal notranslate"><span class="pre">(priority_number,</span> <span class="pre">data)</span></code> 形式的元组。</p>
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</dd></dl>
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</section>
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<section id="lifo-queue">
|
||
<h2>后进先出队列<a class="headerlink" href="#lifo-queue" title="永久链接至标题">¶</a></h2>
|
||
<dl class="class">
|
||
<dt id="asyncio.LifoQueue">
|
||
<em class="property">class </em><code class="sig-prename descclassname">asyncio.</code><code class="sig-name descname">LifoQueue</code><a class="headerlink" href="#asyncio.LifoQueue" title="永久链接至目标">¶</a></dt>
|
||
<dd><p><a class="reference internal" href="#asyncio.Queue" title="asyncio.Queue"><code class="xref py py-class docutils literal notranslate"><span class="pre">Queue</span></code></a> 的变体，先取出最近添加的条目（后进，先出）。</p>
|
||
</dd></dl>
|
||
|
||
</section>
|
||
<section id="exceptions">
|
||
<h2>异常<a class="headerlink" href="#exceptions" title="永久链接至标题">¶</a></h2>
|
||
<dl class="exception">
|
||
<dt id="asyncio.QueueEmpty">
|
||
<em class="property">exception </em><code class="sig-prename descclassname">asyncio.</code><code class="sig-name descname">QueueEmpty</code><a class="headerlink" href="#asyncio.QueueEmpty" title="永久链接至目标">¶</a></dt>
|
||
<dd><p>当队列为空的时候，调用 <a class="reference internal" href="#asyncio.Queue.get_nowait" title="asyncio.Queue.get_nowait"><code class="xref py py-meth docutils literal notranslate"><span class="pre">get_nowait()</span></code></a> 方法而引发这个异常。</p>
|
||
</dd></dl>
|
||
|
||
<dl class="exception">
|
||
<dt id="asyncio.QueueFull">
|
||
<em class="property">exception </em><code class="sig-prename descclassname">asyncio.</code><code class="sig-name descname">QueueFull</code><a class="headerlink" href="#asyncio.QueueFull" title="永久链接至目标">¶</a></dt>
|
||
<dd><p>当队列中条目数量已经达到它的 <em>maxsize</em> 的时候，调用 <a class="reference internal" href="#asyncio.Queue.put_nowait" title="asyncio.Queue.put_nowait"><code class="xref py py-meth docutils literal notranslate"><span class="pre">put_nowait()</span></code></a> 方法而引发的异常。</p>
|
||
</dd></dl>
|
||
|
||
</section>
|
||
<section id="examples">
|
||
<h2>例子<a class="headerlink" href="#examples" title="永久链接至标题">¶</a></h2>
|
||
<p id="asyncio-example-queue-dist">队列能被用于多个的并发任务的工作量分配：</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">asyncio</span>
|
||
<span class="kn">import</span> <span class="nn">random</span>
|
||
<span class="kn">import</span> <span class="nn">time</span>
|
||
|
||
|
||
<span class="k">async</span> <span class="k">def</span> <span class="nf">worker</span><span class="p">(</span><span class="n">name</span><span class="p">,</span> <span class="n">queue</span><span class="p">):</span>
|
||
<span class="k">while</span> <span class="kc">True</span><span class="p">:</span>
|
||
<span class="c1"># Get a "work item" out of the queue.</span>
|
||
<span class="n">sleep_for</span> <span class="o">=</span> <span class="k">await</span> <span class="n">queue</span><span class="o">.</span><span class="n">get</span><span class="p">()</span>
|
||
|
||
<span class="c1"># Sleep for the "sleep_for" seconds.</span>
|
||
<span class="k">await</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">sleep</span><span class="p">(</span><span class="n">sleep_for</span><span class="p">)</span>
|
||
|
||
<span class="c1"># Notify the queue that the "work item" has been processed.</span>
|
||
<span class="n">queue</span><span class="o">.</span><span class="n">task_done</span><span class="p">()</span>
|
||
|
||
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s1">'</span><span class="si">{</span><span class="n">name</span><span class="si">}</span><span class="s1"> has slept for </span><span class="si">{</span><span class="n">sleep_for</span><span class="si">:</span><span class="s1">.2f</span><span class="si">}</span><span class="s1"> seconds'</span><span class="p">)</span>
|
||
|
||
|
||
<span class="k">async</span> <span class="k">def</span> <span class="nf">main</span><span class="p">():</span>
|
||
<span class="c1"># Create a queue that we will use to store our "workload".</span>
|
||
<span class="n">queue</span> <span class="o">=</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">Queue</span><span class="p">()</span>
|
||
|
||
<span class="c1"># Generate random timings and put them into the queue.</span>
|
||
<span class="n">total_sleep_time</span> <span class="o">=</span> <span class="mi">0</span>
|
||
<span class="k">for</span> <span class="n">_</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">20</span><span class="p">):</span>
|
||
<span class="n">sleep_for</span> <span class="o">=</span> <span class="n">random</span><span class="o">.</span><span class="n">uniform</span><span class="p">(</span><span class="mf">0.05</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">)</span>
|
||
<span class="n">total_sleep_time</span> <span class="o">+=</span> <span class="n">sleep_for</span>
|
||
<span class="n">queue</span><span class="o">.</span><span class="n">put_nowait</span><span class="p">(</span><span class="n">sleep_for</span><span class="p">)</span>
|
||
|
||
<span class="c1"># Create three worker tasks to process the queue concurrently.</span>
|
||
<span class="n">tasks</span> <span class="o">=</span> <span class="p">[]</span>
|
||
<span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">3</span><span class="p">):</span>
|
||
<span class="n">task</span> <span class="o">=</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">create_task</span><span class="p">(</span><span class="n">worker</span><span class="p">(</span><span class="sa">f</span><span class="s1">'worker-</span><span class="si">{</span><span class="n">i</span><span class="si">}</span><span class="s1">'</span><span class="p">,</span> <span class="n">queue</span><span class="p">))</span>
|
||
<span class="n">tasks</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">task</span><span class="p">)</span>
|
||
|
||
<span class="c1"># Wait until the queue is fully processed.</span>
|
||
<span class="n">started_at</span> <span class="o">=</span> <span class="n">time</span><span class="o">.</span><span class="n">monotonic</span><span class="p">()</span>
|
||
<span class="k">await</span> <span class="n">queue</span><span class="o">.</span><span class="n">join</span><span class="p">()</span>
|
||
<span class="n">total_slept_for</span> <span class="o">=</span> <span class="n">time</span><span class="o">.</span><span class="n">monotonic</span><span class="p">()</span> <span class="o">-</span> <span class="n">started_at</span>
|
||
|
||
<span class="c1"># Cancel our worker tasks.</span>
|
||
<span class="k">for</span> <span class="n">task</span> <span class="ow">in</span> <span class="n">tasks</span><span class="p">:</span>
|
||
<span class="n">task</span><span class="o">.</span><span class="n">cancel</span><span class="p">()</span>
|
||
<span class="c1"># Wait until all worker tasks are cancelled.</span>
|
||
<span class="k">await</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">gather</span><span class="p">(</span><span class="o">*</span><span class="n">tasks</span><span class="p">,</span> <span class="n">return_exceptions</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
|
||
|
||
<span class="nb">print</span><span class="p">(</span><span class="s1">'===='</span><span class="p">)</span>
|
||
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s1">'3 workers slept in parallel for </span><span class="si">{</span><span class="n">total_slept_for</span><span class="si">:</span><span class="s1">.2f</span><span class="si">}</span><span class="s1"> seconds'</span><span class="p">)</span>
|
||
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s1">'total expected sleep time: </span><span class="si">{</span><span class="n">total_sleep_time</span><span class="si">:</span><span class="s1">.2f</span><span class="si">}</span><span class="s1"> seconds'</span><span class="p">)</span>
|
||
|
||
|
||
<span class="n">asyncio</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="n">main</span><span class="p">())</span>
|
||
</pre></div>
|
||
</div>
|
||
</section>
|
||
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<h3><a href="../contents.html">目录</a></h3>
|
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<ul>
|
||
<li><a class="reference internal" href="#">队列集</a><ul>
|
||
<li><a class="reference internal" href="#queue">Queue</a></li>
|
||
<li><a class="reference internal" href="#priority-queue">优先级队列</a></li>
|
||
<li><a class="reference internal" href="#lifo-queue">后进先出队列</a></li>
|
||
<li><a class="reference internal" href="#exceptions">异常</a></li>
|
||
<li><a class="reference internal" href="#examples">例子</a></li>
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