436 lines
35 KiB
HTML
436 lines
35 KiB
HTML
|
||
<!DOCTYPE html>
|
||
|
||
<html xmlns="http://www.w3.org/1999/xhtml" lang="zh_CN">
|
||
<head>
|
||
<meta charset="utf-8" /><meta name="generator" content="Docutils 0.17.1: http://docutils.sourceforge.net/" />
|
||
|
||
<title>用 asyncio 开发 — Python 3.8.20 文档</title><meta name="viewport" content="width=device-width, initial-scale=1.0">
|
||
|
||
<link rel="stylesheet" href="../_static/pydoctheme.css" type="text/css" />
|
||
<link rel="stylesheet" href="../_static/pygments.css" type="text/css" />
|
||
|
||
<script id="documentation_options" data-url_root="../" src="../_static/documentation_options.js"></script>
|
||
<script src="../_static/jquery.js"></script>
|
||
<script src="../_static/underscore.js"></script>
|
||
<script src="../_static/doctools.js"></script>
|
||
<script src="../_static/language_data.js"></script>
|
||
<script src="../_static/translations.js"></script>
|
||
|
||
<script src="../_static/sidebar.js"></script>
|
||
|
||
<link rel="search" type="application/opensearchdescription+xml"
|
||
title="在 Python 3.8.20 文档 中搜索"
|
||
href="../_static/opensearch.xml"/>
|
||
<link rel="author" title="关于这些文档" href="../about.html" />
|
||
<link rel="index" title="索引" href="../genindex.html" />
|
||
<link rel="search" title="搜索" href="../search.html" />
|
||
<link rel="copyright" title="版权所有" href="../copyright.html" />
|
||
<link rel="next" title="socket --- 底层网络接口" href="socket.html" />
|
||
<link rel="prev" title="底层API目录" href="asyncio-llapi-index.html" />
|
||
<link rel="canonical" href="https://docs.python.org/3/library/asyncio-dev.html" />
|
||
|
||
|
||
|
||
|
||
|
||
<style>
|
||
@media only screen {
|
||
table.full-width-table {
|
||
width: 100%;
|
||
}
|
||
}
|
||
</style>
|
||
<link rel="shortcut icon" type="image/png" href="../_static/py.svg" />
|
||
<script type="text/javascript" src="../_static/copybutton.js"></script>
|
||
<script type="text/javascript" src="../_static/menu.js"></script>
|
||
|
||
</head>
|
||
<body>
|
||
<div class="mobile-nav">
|
||
<input type="checkbox" id="menuToggler" class="toggler__input" aria-controls="navigation"
|
||
aria-pressed="false" aria-expanded="false" role="button" aria-label="Menu" />
|
||
<label for="menuToggler" class="toggler__label">
|
||
<span></span>
|
||
</label>
|
||
<nav class="nav-content" role="navigation">
|
||
<a href="https://www.python.org/" class="nav-logo">
|
||
<img src="../_static/py.svg" alt="Logo"/>
|
||
</a>
|
||
<div class="version_switcher_placeholder"></div>
|
||
<form role="search" class="search" action="../search.html" method="get">
|
||
<svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" viewBox="0 0 24 24" class="search-icon">
|
||
<path fill-rule="nonzero"
|
||
d="M15.5 14h-.79l-.28-.27a6.5 6.5 0 001.48-5.34c-.47-2.78-2.79-5-5.59-5.34a6.505 6.505 0 00-7.27 7.27c.34 2.8 2.56 5.12 5.34 5.59a6.5 6.5 0 005.34-1.48l.27.28v.79l4.25 4.25c.41.41 1.08.41 1.49 0 .41-.41.41-1.08 0-1.49L15.5 14zm-6 0C7.01 14 5 11.99 5 9.5S7.01 5 9.5 5 14 7.01 14 9.5 11.99 14 9.5 14z" fill="#444"></path>
|
||
</svg>
|
||
<input type="text" name="q" aria-label="快速搜索"/>
|
||
<input type="submit" value="转向"/>
|
||
</form>
|
||
</nav>
|
||
<div class="menu-wrapper">
|
||
<nav class="menu" role="navigation" aria-label="main navigation">
|
||
<div class="language_switcher_placeholder"></div>
|
||
<h3><a href="../contents.html">目录</a></h3>
|
||
<ul>
|
||
<li><a class="reference internal" href="#">用 asyncio 开发</a><ul>
|
||
<li><a class="reference internal" href="#debug-mode">Debug 模式</a></li>
|
||
<li><a class="reference internal" href="#concurrency-and-multithreading">并发性和多线程</a></li>
|
||
<li><a class="reference internal" href="#running-blocking-code">运行阻塞的代码</a></li>
|
||
<li><a class="reference internal" href="#logging">日志记录</a></li>
|
||
<li><a class="reference internal" href="#detect-never-awaited-coroutines">检测 never-awaited 协同程序</a></li>
|
||
<li><a class="reference internal" href="#detect-never-retrieved-exceptions">检测就再也没异常</a></li>
|
||
</ul>
|
||
</li>
|
||
</ul>
|
||
|
||
<h4>上一个主题</h4>
|
||
<p class="topless"><a href="asyncio-llapi-index.html"
|
||
title="上一章">底层API目录</a></p>
|
||
<h4>下一个主题</h4>
|
||
<p class="topless"><a href="socket.html"
|
||
title="下一章"><code class="xref py py-mod docutils literal notranslate"><span class="pre">socket</span></code> --- 底层网络接口</a></p>
|
||
<div role="note" aria-label="source link">
|
||
<h3>本页</h3>
|
||
<ul class="this-page-menu">
|
||
<li><a href="../bugs.html">报告 Bug</a></li>
|
||
<li>
|
||
<a href="https://github.com/python/cpython/blob/3.8/Doc/library/asyncio-dev.rst"
|
||
rel="nofollow">显示源代码
|
||
</a>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
</nav>
|
||
</div>
|
||
</div>
|
||
|
||
<div id="outdated-warning" style="padding: .5em; text-align: center; background-color: #FFBABA; color: #6A0E0E;">
|
||
这个文档所针对的是一个已不再受支持的 Python 旧版本。
|
||
你应当升级版本，并阅读
|
||
<a href="/3/library/asyncio-dev.html"> Python 当前稳定版本的文档</a>.
|
||
</div>
|
||
|
||
<div class="related" role="navigation" aria-label="related navigation">
|
||
<h3>导航</h3>
|
||
<ul>
|
||
<li class="right" style="margin-right: 10px">
|
||
<a href="../genindex.html" title="总目录"
|
||
accesskey="I">索引</a></li>
|
||
<li class="right" >
|
||
<a href="../py-modindex.html" title="Python 模块索引"
|
||
>模块</a> |</li>
|
||
<li class="right" >
|
||
<a href="socket.html" title="socket --- 底层网络接口"
|
||
accesskey="N">下一页</a> |</li>
|
||
<li class="right" >
|
||
<a href="asyncio-llapi-index.html" title="底层API目录"
|
||
accesskey="P">上一页</a> |</li>
|
||
|
||
<li><img src="../_static/py.svg" alt="python logo" style="vertical-align: middle; margin-top: -1px"/></li>
|
||
<li><a href="https://www.python.org/">Python</a> »</li>
|
||
<li class="switchers">
|
||
<div class="language_switcher_placeholder"></div>
|
||
<div class="version_switcher_placeholder"></div>
|
||
</li>
|
||
<li>
|
||
|
||
</li>
|
||
<li id="cpython-language-and-version">
|
||
<a href="../index.html">3.8.20 Documentation</a> »
|
||
</li>
|
||
|
||
<li class="nav-item nav-item-1"><a href="index.html" >Python 标准库</a> »</li>
|
||
<li class="nav-item nav-item-2"><a href="ipc.html" >网络和进程间通信</a> »</li>
|
||
<li class="nav-item nav-item-3"><a href="asyncio.html" accesskey="U"><code class="xref py py-mod docutils literal notranslate"><span class="pre">asyncio</span></code> --- 异步 I/O</a> »</li>
|
||
<li class="right">
|
||
|
||
|
||
<div class="inline-search" role="search">
|
||
<form class="inline-search" action="../search.html" method="get">
|
||
<input placeholder="快速搜索" aria-label="快速搜索" type="text" name="q" />
|
||
<input type="submit" value="转向" />
|
||
<input type="hidden" name="check_keywords" value="yes" />
|
||
<input type="hidden" name="area" value="default" />
|
||
</form>
|
||
</div>
|
||
|
|
||
</li>
|
||
|
||
</ul>
|
||
</div>
|
||
|
||
<div class="document">
|
||
<div class="documentwrapper">
|
||
<div class="bodywrapper">
|
||
<div class="body" role="main">
|
||
|
||
<section id="developing-with-asyncio">
|
||
<span id="asyncio-dev"></span><h1>用 asyncio 开发<a class="headerlink" href="#developing-with-asyncio" title="永久链接至标题">¶</a></h1>
|
||
<p>异步编程与传统的“顺序”编程不同。</p>
|
||
<p>本页列出常见的错误和陷阱，并解释如何避免它们。</p>
|
||
<section id="debug-mode">
|
||
<span id="asyncio-debug-mode"></span><h2>Debug 模式<a class="headerlink" href="#debug-mode" title="永久链接至标题">¶</a></h2>
|
||
<p>默认情况下，asyncio以生产模式运行。为了简化开发，asyncio还有一种*debug 模式* 。</p>
|
||
<p>有几种方法可以启用异步调试模式:</p>
|
||
<ul class="simple">
|
||
<li><p>将 <span class="target" id="index-2"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONASYNCIODEBUG"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONASYNCIODEBUG</span></code></a> 环境变量设置为 <code class="docutils literal notranslate"><span class="pre">1</span></code> 。</p></li>
|
||
<li><p>使用 <a class="reference internal" href="../using/cmdline.html#id5"><code class="xref std std-option docutils literal notranslate"><span class="pre">-X</span></code></a> <code class="docutils literal notranslate"><span class="pre">dev</span></code> Python 命令行选项。</p></li>
|
||
<li><p>将 <code class="docutils literal notranslate"><span class="pre">debug=True</span></code> 传递给 <a class="reference internal" href="asyncio-task.html#asyncio.run" title="asyncio.run"><code class="xref py py-func docutils literal notranslate"><span class="pre">asyncio.run()</span></code></a> 。</p></li>
|
||
<li><p>调用 <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.set_debug" title="asyncio.loop.set_debug"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.set_debug()</span></code></a> 。</p></li>
|
||
</ul>
|
||
<p>除了启用调试模式外，还要考虑:</p>
|
||
<ul>
|
||
<li><p>将 <a class="reference internal" href="#asyncio-logger"><span class="std std-ref">asyncio logger</span></a> 的日志级别设置为 <code class="xref py py-data docutils literal notranslate"><span class="pre">logging.DEBUG</span></code>，例如，下面的代码片段可以在应用程序启动时运行:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">logging</span><span class="o">.</span><span class="n">basicConfig</span><span class="p">(</span><span class="n">level</span><span class="o">=</span><span class="n">logging</span><span class="o">.</span><span class="n">DEBUG</span><span class="p">)</span>
|
||
</pre></div>
|
||
</div>
|
||
</li>
|
||
<li><p>配置 <a class="reference internal" href="warnings.html#module-warnings" title="warnings: Issue warning messages and control their disposition."><code class="xref py py-mod docutils literal notranslate"><span class="pre">warnings</span></code></a> 模块以显示 <a class="reference internal" href="exceptions.html#ResourceWarning" title="ResourceWarning"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ResourceWarning</span></code></a> 警告。一种方法是使用 <a class="reference internal" href="../using/cmdline.html#cmdoption-w"><code class="xref std std-option docutils literal notranslate"><span class="pre">-W</span></code></a> <code class="docutils literal notranslate"><span class="pre">default</span></code> 命令行选项。</p></li>
|
||
</ul>
|
||
<p>启用调试模式时:</p>
|
||
<ul class="simple">
|
||
<li><p>asyncio 检查 <a class="reference internal" href="#asyncio-coroutine-not-scheduled"><span class="std std-ref">未被等待的协程</span></a> 并记录他们；这将消除“被遗忘的等待”问题。</p></li>
|
||
<li><p>许多非线程安全的异步 APIs (例如 <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.call_soon" title="asyncio.loop.call_soon"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.call_soon()</span></code></a> 和 <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.call_at" title="asyncio.loop.call_at"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.call_at()</span></code></a> 方法)，如果从错误的线程调用，则会引发异常。</p></li>
|
||
<li><p>如果执行I/O操作花费的时间太长，则记录I/O选择器的执行时间。</p></li>
|
||
<li><p>执行时间超过100毫秒的回调将会载入日志。 属性 <code class="xref py py-attr docutils literal notranslate"><span class="pre">loop.slow_callback_duration</span></code> 可用于设置以秒为单位的最小执行持续时间，这被视为“缓慢”。</p></li>
|
||
</ul>
|
||
</section>
|
||
<section id="concurrency-and-multithreading">
|
||
<span id="asyncio-multithreading"></span><h2>并发性和多线程<a class="headerlink" href="#concurrency-and-multithreading" title="永久链接至标题">¶</a></h2>
|
||
<p>事件循环在线程中运行(通常是主线程)，并在其线程中执行所有回调和任务。当一个任务在事件循环中运行时，没有其他任务可以在同一个线程中运行。当一个任务执行一个 <code class="docutils literal notranslate"><span class="pre">await</span></code> 表达式时，正在运行的任务被挂起，事件循环执行下一个任务。</p>
|
||
<p>要调度来自另一 OS 线程的 <a class="reference internal" href="../glossary.html#term-callback"><span class="xref std std-term">callback</span></a>，应该使用 <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.call_soon_threadsafe" title="asyncio.loop.call_soon_threadsafe"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.call_soon_threadsafe()</span></code></a> 方法。 例如:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">loop</span><span class="o">.</span><span class="n">call_soon_threadsafe</span><span class="p">(</span><span class="n">callback</span><span class="p">,</span> <span class="o">*</span><span class="n">args</span><span class="p">)</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>几乎所有异步对象都不是线程安全的，这通常不是问题，除非在任务或回调函数之外有代码可以使用它们。如果需要这样的代码来调用低级异步API，应该使用 <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.call_soon_threadsafe" title="asyncio.loop.call_soon_threadsafe"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.call_soon_threadsafe()</span></code></a> 方法，例如:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">loop</span><span class="o">.</span><span class="n">call_soon_threadsafe</span><span class="p">(</span><span class="n">fut</span><span class="o">.</span><span class="n">cancel</span><span class="p">)</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>要从不同的OS线程调度一个协程对象，应该使用 <a class="reference internal" href="asyncio-task.html#asyncio.run_coroutine_threadsafe" title="asyncio.run_coroutine_threadsafe"><code class="xref py py-func docutils literal notranslate"><span class="pre">run_coroutine_threadsafe()</span></code></a> 函数。它返回一个 <a class="reference internal" href="concurrent.futures.html#concurrent.futures.Future" title="concurrent.futures.Future"><code class="xref py py-class docutils literal notranslate"><span class="pre">concurrent.futures.Future</span></code></a> 。查询结果:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">async</span> <span class="k">def</span> <span class="nf">coro_func</span><span class="p">():</span>
|
||
<span class="k">return</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="mi">1</span><span class="p">,</span> <span class="mi">42</span><span class="p">)</span>
|
||
|
||
<span class="c1"># Later in another OS thread:</span>
|
||
|
||
<span class="n">future</span> <span class="o">=</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">run_coroutine_threadsafe</span><span class="p">(</span><span class="n">coro_func</span><span class="p">(),</span> <span class="n">loop</span><span class="p">)</span>
|
||
<span class="c1"># Wait for the result:</span>
|
||
<span class="n">result</span> <span class="o">=</span> <span class="n">future</span><span class="o">.</span><span class="n">result</span><span class="p">()</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>为了能够处理信号和执行子进程，事件循环必须运行于主线程中。</p>
|
||
<p>方法 <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.run_in_executor" title="asyncio.loop.run_in_executor"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.run_in_executor()</span></code></a> 可以和 <a class="reference internal" href="concurrent.futures.html#concurrent.futures.ThreadPoolExecutor" title="concurrent.futures.ThreadPoolExecutor"><code class="xref py py-class docutils literal notranslate"><span class="pre">concurrent.futures.ThreadPoolExecutor</span></code></a> 一起使用，用于在一个不同的操作系统线程中执行阻塞代码，并避免阻塞运行事件循环的那个操作系统线程。</p>
|
||
<p>目前没有什么办法能直接从另一个进程 (例如通过 <a class="reference internal" href="multiprocessing.html#module-multiprocessing" title="multiprocessing: Process-based parallelism."><code class="xref py py-mod docutils literal notranslate"><span class="pre">multiprocessing</span></code></a> 启动的进程) 安排协程或回调。 <a class="reference internal" href="asyncio-eventloop.html#asyncio-event-loop"><span class="std std-ref">事件循环方法</span></a> 小节列出了可以从管道读取并监视文件描述符而不会阻塞事件循环的 API。 此外，asyncio 的 <a class="reference internal" href="asyncio-subprocess.html#asyncio-subprocess"><span class="std std-ref">子进程</span></a> API 提供了一种启动进程并从事件循环与其通信的办法。 最后，之前提到的 <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.run_in_executor" title="asyncio.loop.run_in_executor"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.run_in_executor()</span></code></a> 方法也可配合 <a class="reference internal" href="concurrent.futures.html#concurrent.futures.ProcessPoolExecutor" title="concurrent.futures.ProcessPoolExecutor"><code class="xref py py-class docutils literal notranslate"><span class="pre">concurrent.futures.ProcessPoolExecutor</span></code></a> 使用以在另一个进程中执行代码。</p>
|
||
</section>
|
||
<section id="running-blocking-code">
|
||
<span id="asyncio-handle-blocking"></span><h2>运行阻塞的代码<a class="headerlink" href="#running-blocking-code" title="永久链接至标题">¶</a></h2>
|
||
<p>不应该直接调用阻塞( CPU 绑定)代码。例如，如果一个函数执行1秒的 CPU 密集型计算，那么所有并发异步任务和 IO 操作都将延迟1秒。</p>
|
||
<p>可以用执行器在不同的线程甚至不同的进程中运行任务，以避免使用事件循环阻塞 OS 线程。 请参阅 <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.run_in_executor" title="asyncio.loop.run_in_executor"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.run_in_executor()</span></code></a> 方法了解详情。</p>
|
||
</section>
|
||
<section id="logging">
|
||
<span id="asyncio-logger"></span><h2>日志记录<a class="headerlink" href="#logging" title="永久链接至标题">¶</a></h2>
|
||
<p>asyncio使用 <a class="reference internal" href="logging.html#module-logging" title="logging: Flexible event logging system for applications."><code class="xref py py-mod docutils literal notranslate"><span class="pre">logging</span></code></a> 模块，所有日志记录都是通过 <code class="docutils literal notranslate"><span class="pre">"asyncio"</span></code> logger执行的。</p>
|
||
<p>默认日志级别是 <code class="xref py py-data docutils literal notranslate"><span class="pre">logging.INFO</span></code> 。可以很容易地调整:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">logging</span><span class="o">.</span><span class="n">getLogger</span><span class="p">(</span><span class="s2">"asyncio"</span><span class="p">)</span><span class="o">.</span><span class="n">setLevel</span><span class="p">(</span><span class="n">logging</span><span class="o">.</span><span class="n">WARNING</span><span class="p">)</span>
|
||
</pre></div>
|
||
</div>
|
||
</section>
|
||
<section id="detect-never-awaited-coroutines">
|
||
<span id="asyncio-coroutine-not-scheduled"></span><h2>检测 never-awaited 协同程序<a class="headerlink" href="#detect-never-awaited-coroutines" title="永久链接至标题">¶</a></h2>
|
||
<p>当协程函数被调用而不是被等待时 (即执行 <code class="docutils literal notranslate"><span class="pre">coro()</span></code> 而不是 <code class="docutils literal notranslate"><span class="pre">await</span> <span class="pre">coro()</span></code>) 或者协程没有通过 <a class="reference internal" href="asyncio-task.html#asyncio.create_task" title="asyncio.create_task"><code class="xref py py-meth docutils literal notranslate"><span class="pre">asyncio.create_task()</span></code></a> 被排入计划日程，asyncio 将会发出一条 <a class="reference internal" href="exceptions.html#RuntimeWarning" title="RuntimeWarning"><code class="xref py py-exc docutils literal notranslate"><span class="pre">RuntimeWarning</span></code></a>:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">asyncio</span>
|
||
|
||
<span class="k">async</span> <span class="k">def</span> <span class="nf">test</span><span class="p">():</span>
|
||
<span class="nb">print</span><span class="p">(</span><span class="s2">"never scheduled"</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="n">test</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>
|
||
<p>输出:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">test</span><span class="o">.</span><span class="n">py</span><span class="p">:</span><span class="mi">7</span><span class="p">:</span> <span class="ne">RuntimeWarning</span><span class="p">:</span> <span class="n">coroutine</span> <span class="s1">'test'</span> <span class="n">was</span> <span class="n">never</span> <span class="n">awaited</span>
|
||
<span class="n">test</span><span class="p">()</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>调试模式的输出:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">test</span><span class="o">.</span><span class="n">py</span><span class="p">:</span><span class="mi">7</span><span class="p">:</span> <span class="ne">RuntimeWarning</span><span class="p">:</span> <span class="n">coroutine</span> <span class="s1">'test'</span> <span class="n">was</span> <span class="n">never</span> <span class="n">awaited</span>
|
||
<span class="n">Coroutine</span> <span class="n">created</span> <span class="n">at</span> <span class="p">(</span><span class="n">most</span> <span class="n">recent</span> <span class="n">call</span> <span class="n">last</span><span class="p">)</span>
|
||
<span class="n">File</span> <span class="s2">"../t.py"</span><span class="p">,</span> <span class="n">line</span> <span class="mi">9</span><span class="p">,</span> <span class="ow">in</span> <span class="o"><</span><span class="n">module</span><span class="o">></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> <span class="n">debug</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
|
||
|
||
<span class="o"><</span> <span class="o">..</span> <span class="o">></span>
|
||
|
||
<span class="n">File</span> <span class="s2">"../t.py"</span><span class="p">,</span> <span class="n">line</span> <span class="mi">7</span><span class="p">,</span> <span class="ow">in</span> <span class="n">main</span>
|
||
<span class="n">test</span><span class="p">()</span>
|
||
<span class="n">test</span><span class="p">()</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>通常的修复方法是等待协程或者调用 <a class="reference internal" href="asyncio-task.html#asyncio.create_task" title="asyncio.create_task"><code class="xref py py-meth docutils literal notranslate"><span class="pre">asyncio.create_task()</span></code></a> 函数:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">async</span> <span class="k">def</span> <span class="nf">main</span><span class="p">():</span>
|
||
<span class="k">await</span> <span class="n">test</span><span class="p">()</span>
|
||
</pre></div>
|
||
</div>
|
||
</section>
|
||
<section id="detect-never-retrieved-exceptions">
|
||
<h2>检测就再也没异常<a class="headerlink" href="#detect-never-retrieved-exceptions" title="永久链接至标题">¶</a></h2>
|
||
<p>如果调用 <a class="reference internal" href="asyncio-future.html#asyncio.Future.set_exception" title="asyncio.Future.set_exception"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Future.set_exception()</span></code></a> ，但不等待 Future 对象，将异常传播到用户代码。在这种情况下，当 Future 对象被垃圾收集时，asyncio将发出一条日志消息。</p>
|
||
<p>未处理异常的例子:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">asyncio</span>
|
||
|
||
<span class="k">async</span> <span class="k">def</span> <span class="nf">bug</span><span class="p">():</span>
|
||
<span class="k">raise</span> <span class="ne">Exception</span><span class="p">(</span><span class="s2">"not consumed"</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="n">asyncio</span><span class="o">.</span><span class="n">create_task</span><span class="p">(</span><span class="n">bug</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>
|
||
<p>输出:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">Task</span> <span class="n">exception</span> <span class="n">was</span> <span class="n">never</span> <span class="n">retrieved</span>
|
||
<span class="n">future</span><span class="p">:</span> <span class="o"><</span><span class="n">Task</span> <span class="n">finished</span> <span class="n">coro</span><span class="o">=<</span><span class="n">bug</span><span class="p">()</span> <span class="n">done</span><span class="p">,</span> <span class="n">defined</span> <span class="n">at</span> <span class="n">test</span><span class="o">.</span><span class="n">py</span><span class="p">:</span><span class="mi">3</span><span class="o">></span>
|
||
<span class="n">exception</span><span class="o">=</span><span class="ne">Exception</span><span class="p">(</span><span class="s1">'not consumed'</span><span class="p">)</span><span class="o">></span>
|
||
|
||
<span class="n">Traceback</span> <span class="p">(</span><span class="n">most</span> <span class="n">recent</span> <span class="n">call</span> <span class="n">last</span><span class="p">):</span>
|
||
<span class="n">File</span> <span class="s2">"test.py"</span><span class="p">,</span> <span class="n">line</span> <span class="mi">4</span><span class="p">,</span> <span class="ow">in</span> <span class="n">bug</span>
|
||
<span class="k">raise</span> <span class="ne">Exception</span><span class="p">(</span><span class="s2">"not consumed"</span><span class="p">)</span>
|
||
<span class="ne">Exception</span><span class="p">:</span> <span class="ow">not</span> <span class="n">consumed</span>
|
||
</pre></div>
|
||
</div>
|
||
<p><a class="reference internal" href="#asyncio-debug-mode"><span class="std std-ref">激活调试模式</span></a> 以获取任务创建处的跟踪信息:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></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> <span class="n">debug</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>调试模式的输出:</p>
|
||
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">Task</span> <span class="n">exception</span> <span class="n">was</span> <span class="n">never</span> <span class="n">retrieved</span>
|
||
<span class="n">future</span><span class="p">:</span> <span class="o"><</span><span class="n">Task</span> <span class="n">finished</span> <span class="n">coro</span><span class="o">=<</span><span class="n">bug</span><span class="p">()</span> <span class="n">done</span><span class="p">,</span> <span class="n">defined</span> <span class="n">at</span> <span class="n">test</span><span class="o">.</span><span class="n">py</span><span class="p">:</span><span class="mi">3</span><span class="o">></span>
|
||
<span class="n">exception</span><span class="o">=</span><span class="ne">Exception</span><span class="p">(</span><span class="s1">'not consumed'</span><span class="p">)</span> <span class="n">created</span> <span class="n">at</span> <span class="n">asyncio</span><span class="o">/</span><span class="n">tasks</span><span class="o">.</span><span class="n">py</span><span class="p">:</span><span class="mi">321</span><span class="o">></span>
|
||
|
||
<span class="n">source_traceback</span><span class="p">:</span> <span class="n">Object</span> <span class="n">created</span> <span class="n">at</span> <span class="p">(</span><span class="n">most</span> <span class="n">recent</span> <span class="n">call</span> <span class="n">last</span><span class="p">):</span>
|
||
<span class="n">File</span> <span class="s2">"../t.py"</span><span class="p">,</span> <span class="n">line</span> <span class="mi">9</span><span class="p">,</span> <span class="ow">in</span> <span class="o"><</span><span class="n">module</span><span class="o">></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> <span class="n">debug</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
|
||
|
||
<span class="o"><</span> <span class="o">..</span> <span class="o">></span>
|
||
|
||
<span class="n">Traceback</span> <span class="p">(</span><span class="n">most</span> <span class="n">recent</span> <span class="n">call</span> <span class="n">last</span><span class="p">):</span>
|
||
<span class="n">File</span> <span class="s2">"../t.py"</span><span class="p">,</span> <span class="n">line</span> <span class="mi">4</span><span class="p">,</span> <span class="ow">in</span> <span class="n">bug</span>
|
||
<span class="k">raise</span> <span class="ne">Exception</span><span class="p">(</span><span class="s2">"not consumed"</span><span class="p">)</span>
|
||
<span class="ne">Exception</span><span class="p">:</span> <span class="ow">not</span> <span class="n">consumed</span>
|
||
</pre></div>
|
||
</div>
|
||
</section>
|
||
</section>
|
||
|
||
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sphinxsidebar" role="navigation" aria-label="main navigation">
|
||
<div class="sphinxsidebarwrapper">
|
||
<h3><a href="../contents.html">目录</a></h3>
|
||
<ul>
|
||
<li><a class="reference internal" href="#">用 asyncio 开发</a><ul>
|
||
<li><a class="reference internal" href="#debug-mode">Debug 模式</a></li>
|
||
<li><a class="reference internal" href="#concurrency-and-multithreading">并发性和多线程</a></li>
|
||
<li><a class="reference internal" href="#running-blocking-code">运行阻塞的代码</a></li>
|
||
<li><a class="reference internal" href="#logging">日志记录</a></li>
|
||
<li><a class="reference internal" href="#detect-never-awaited-coroutines">检测 never-awaited 协同程序</a></li>
|
||
<li><a class="reference internal" href="#detect-never-retrieved-exceptions">检测就再也没异常</a></li>
|
||
</ul>
|
||
</li>
|
||
</ul>
|
||
|
||
<h4>上一个主题</h4>
|
||
<p class="topless"><a href="asyncio-llapi-index.html"
|
||
title="上一章">底层API目录</a></p>
|
||
<h4>下一个主题</h4>
|
||
<p class="topless"><a href="socket.html"
|
||
title="下一章"><code class="xref py py-mod docutils literal notranslate"><span class="pre">socket</span></code> --- 底层网络接口</a></p>
|
||
<div role="note" aria-label="source link">
|
||
<h3>本页</h3>
|
||
<ul class="this-page-menu">
|
||
<li><a href="../bugs.html">报告 Bug</a></li>
|
||
<li>
|
||
<a href="https://github.com/python/cpython/blob/3.8/Doc/library/asyncio-dev.rst"
|
||
rel="nofollow">显示源代码
|
||
</a>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="clearer"></div>
|
||
</div>
|
||
<div class="related" role="navigation" aria-label="related navigation">
|
||
<h3>导航</h3>
|
||
<ul>
|
||
<li class="right" style="margin-right: 10px">
|
||
<a href="../genindex.html" title="总目录"
|
||
>索引</a></li>
|
||
<li class="right" >
|
||
<a href="../py-modindex.html" title="Python 模块索引"
|
||
>模块</a> |</li>
|
||
<li class="right" >
|
||
<a href="socket.html" title="socket --- 底层网络接口"
|
||
>下一页</a> |</li>
|
||
<li class="right" >
|
||
<a href="asyncio-llapi-index.html" title="底层API目录"
|
||
>上一页</a> |</li>
|
||
|
||
<li><img src="../_static/py.svg" alt="python logo" style="vertical-align: middle; margin-top: -1px"/></li>
|
||
<li><a href="https://www.python.org/">Python</a> »</li>
|
||
<li class="switchers">
|
||
<div class="language_switcher_placeholder"></div>
|
||
<div class="version_switcher_placeholder"></div>
|
||
</li>
|
||
<li>
|
||
|
||
</li>
|
||
<li id="cpython-language-and-version">
|
||
<a href="../index.html">3.8.20 Documentation</a> »
|
||
</li>
|
||
|
||
<li class="nav-item nav-item-1"><a href="index.html" >Python 标准库</a> »</li>
|
||
<li class="nav-item nav-item-2"><a href="ipc.html" >网络和进程间通信</a> »</li>
|
||
<li class="nav-item nav-item-3"><a href="asyncio.html" ><code class="xref py py-mod docutils literal notranslate"><span class="pre">asyncio</span></code> --- 异步 I/O</a> »</li>
|
||
<li class="right">
|
||
|
||
|
||
<div class="inline-search" role="search">
|
||
<form class="inline-search" action="../search.html" method="get">
|
||
<input placeholder="快速搜索" aria-label="快速搜索" type="text" name="q" />
|
||
<input type="submit" value="转向" />
|
||
<input type="hidden" name="check_keywords" value="yes" />
|
||
<input type="hidden" name="area" value="default" />
|
||
</form>
|
||
</div>
|
||
|
|
||
</li>
|
||
|
||
</ul>
|
||
</div>
|
||
<div class="footer">
|
||
© <a href="../copyright.html">版权所有</a> 2001-2024, Python Software Foundation.
|
||
<br />
|
||
This page is licensed under the Python Software Foundation License Version 2.
|
||
<br />
|
||
Examples, recipes, and other code in the documentation are additionally licensed under the Zero Clause BSD License.
|
||
<br />
|
||
|
||
<br />
|
||
|
||
The Python Software Foundation is a non-profit corporation.
|
||
<a href="https://www.python.org/psf/donations/">Please donate.</a>
|
||
<br />
|
||
<br />
|
||
|
||
最后更新于 12月 09, 2024.
|
||
<a href="https://docs.python.org/3/bugs.html">Found a bug</a>?
|
||
<br />
|
||
|
||
Created using <a href="https://www.sphinx-doc.org/">Sphinx</a> 2.4.4.
|
||
</div>
|
||
|
||
</body>
|
||
</html> |