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  98. <li><a class="reference internal" href="#">Subprocesses</a><ul>

  99. <li><a class="reference internal" href="#creating-subprocesses">Creating Subprocesses</a></li>

  100. <li><a class="reference internal" href="#constants">Constants</a></li>

  101. <li><a class="reference internal" href="#interacting-with-subprocesses">Interacting with Subprocesses</a><ul>

  102. <li><a class="reference internal" href="#subprocess-and-threads">Subprocess and Threads</a></li>

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  199.   <section id="subprocesses">

  200. <span id="asyncio-subprocess"></span><h1>Subprocesses<a class="headerlink" href="#subprocesses" title="Link to this heading">¶</a></h1>

  201. <p><strong>Source code:</strong> <a class="reference external" href="https://github.com/python/cpython/tree/3.12/Lib/asyncio/subprocess.py">Lib/asyncio/subprocess.py</a>,

  202. <a class="reference external" href="https://github.com/python/cpython/tree/3.12/Lib/asyncio/base_subprocess.py">Lib/asyncio/base_subprocess.py</a></p>

  203. <hr class="docutils" />

  204. <p>This section describes high-level async/await asyncio APIs to

  205. create and manage subprocesses.</p>

  206. <p id="asyncio-example-subprocess-shell">Here’s an example of how asyncio can run a shell command and

  207. obtain its result:</p>

  208. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">asyncio</span>

  209. 

  210. <span class="k">async</span> <span class="k">def</span> <span class="nf">run</span><span class="p">(</span><span class="n">cmd</span><span class="p">):</span>

  211.     <span class="n">proc</span> <span class="o">=</span> <span class="k">await</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">create_subprocess_shell</span><span class="p">(</span>

  212.         <span class="n">cmd</span><span class="p">,</span>

  213.         <span class="n">stdout</span><span class="o">=</span><span class="n">asyncio</span><span class="o">.</span><span class="n">subprocess</span><span class="o">.</span><span class="n">PIPE</span><span class="p">,</span>

  214.         <span class="n">stderr</span><span class="o">=</span><span class="n">asyncio</span><span class="o">.</span><span class="n">subprocess</span><span class="o">.</span><span class="n">PIPE</span><span class="p">)</span>

  215. 

  216.     <span class="n">stdout</span><span class="p">,</span> <span class="n">stderr</span> <span class="o">=</span> <span class="k">await</span> <span class="n">proc</span><span class="o">.</span><span class="n">communicate</span><span class="p">()</span>

  217. 

  218.     <span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s1">&#39;[</span><span class="si">{</span><span class="n">cmd</span><span class="si">!r}</span><span class="s1"> exited with </span><span class="si">{</span><span class="n">proc</span><span class="o">.</span><span class="n">returncode</span><span class="si">}</span><span class="s1">]&#39;</span><span class="p">)</span>

  219.     <span class="k">if</span> <span class="n">stdout</span><span class="p">:</span>

  220.         <span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s1">&#39;[stdout]</span><span class="se">\n</span><span class="si">{</span><span class="n">stdout</span><span class="o">.</span><span class="n">decode</span><span class="p">()</span><span class="si">}</span><span class="s1">&#39;</span><span class="p">)</span>

  221.     <span class="k">if</span> <span class="n">stderr</span><span class="p">:</span>

  222.         <span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s1">&#39;[stderr]</span><span class="se">\n</span><span class="si">{</span><span class="n">stderr</span><span class="o">.</span><span class="n">decode</span><span class="p">()</span><span class="si">}</span><span class="s1">&#39;</span><span class="p">)</span>

  223. 

  224. <span class="n">asyncio</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="n">run</span><span class="p">(</span><span class="s1">&#39;ls /zzz&#39;</span><span class="p">))</span>

  225. </pre></div>

  226. </div>

  227. <p>will print:</p>

  228. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="p">[</span><span class="s1">&#39;ls /zzz&#39;</span> <span class="n">exited</span> <span class="k">with</span> <span class="mi">1</span><span class="p">]</span>

  229. <span class="p">[</span><span class="n">stderr</span><span class="p">]</span>

  230. <span class="n">ls</span><span class="p">:</span> <span class="o">/</span><span class="n">zzz</span><span class="p">:</span> <span class="n">No</span> <span class="n">such</span> <span class="n">file</span> <span class="ow">or</span> <span class="n">directory</span>

  231. </pre></div>

  232. </div>

  233. <p>Because all asyncio subprocess functions are asynchronous and asyncio

  234. provides many tools to work with such functions, it is easy to execute

  235. and monitor multiple subprocesses in parallel.  It is indeed trivial

  236. to modify the above example to run several commands simultaneously:</p>

  237. <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>

  238.     <span class="k">await</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">gather</span><span class="p">(</span>

  239.         <span class="n">run</span><span class="p">(</span><span class="s1">&#39;ls /zzz&#39;</span><span class="p">),</span>

  240.         <span class="n">run</span><span class="p">(</span><span class="s1">&#39;sleep 1; echo &quot;hello&quot;&#39;</span><span class="p">))</span>

  241. 

  242. <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>

  243. </pre></div>

  244. </div>

  245. <p>See also the <a class="reference internal" href="#examples">Examples</a> subsection.</p>

  246. <section id="creating-subprocesses">

  247. <h2>Creating Subprocesses<a class="headerlink" href="#creating-subprocesses" title="Link to this heading">¶</a></h2>

  248. <dl class="py function">

  249. <dt class="sig sig-object py" id="asyncio.create_subprocess_exec">

  250. <em class="property"><span class="pre">coroutine</span> </em><span class="sig-prename descclassname"><span class="pre">asyncio.</span></span><span class="sig-name descname"><span class="pre">create_subprocess_exec</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">program</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span><span class="n"><span class="pre">args</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stdin</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stdout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stderr</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">limit</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">**</span></span><span class="n"><span class="pre">kwds</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.create_subprocess_exec" title="Link to this definition">¶</a></dt>

  251. <dd><p>Create a subprocess.</p>

  252. <p>The <em>limit</em> argument sets the buffer limit for <a class="reference internal" href="asyncio-stream.html#asyncio.StreamReader" title="asyncio.StreamReader"><code class="xref py py-class docutils literal notranslate"><span class="pre">StreamReader</span></code></a>

  253. wrappers for <code class="xref py py-attr docutils literal notranslate"><span class="pre">Process.stdout</span></code> and <code class="xref py py-attr docutils literal notranslate"><span class="pre">Process.stderr</span></code>

  254. (if <a class="reference internal" href="subprocess.html#subprocess.PIPE" title="subprocess.PIPE"><code class="xref py py-const docutils literal notranslate"><span class="pre">subprocess.PIPE</span></code></a> is passed to <em>stdout</em> and <em>stderr</em> arguments).</p>

  255. <p>Return a <a class="reference internal" href="#asyncio.subprocess.Process" title="asyncio.subprocess.Process"><code class="xref py py-class docutils literal notranslate"><span class="pre">Process</span></code></a> instance.</p>

  256. <p>See the documentation of <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.subprocess_exec" title="asyncio.loop.subprocess_exec"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.subprocess_exec()</span></code></a> for other

  257. parameters.</p>

  258. <div class="versionchanged">

  259. <p><span class="versionmodified changed">Changed in version 3.10: </span>Removed the <em>loop</em> parameter.</p>

  260. </div>

  261. </dd></dl>

  262. 

  263. <dl class="py function">

  264. <dt class="sig sig-object py" id="asyncio.create_subprocess_shell">

  265. <em class="property"><span class="pre">coroutine</span> </em><span class="sig-prename descclassname"><span class="pre">asyncio.</span></span><span class="sig-name descname"><span class="pre">create_subprocess_shell</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">cmd</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stdin</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stdout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stderr</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">limit</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">**</span></span><span class="n"><span class="pre">kwds</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.create_subprocess_shell" title="Link to this definition">¶</a></dt>

  266. <dd><p>Run the <em>cmd</em> shell command.</p>

  267. <p>The <em>limit</em> argument sets the buffer limit for <a class="reference internal" href="asyncio-stream.html#asyncio.StreamReader" title="asyncio.StreamReader"><code class="xref py py-class docutils literal notranslate"><span class="pre">StreamReader</span></code></a>

  268. wrappers for <code class="xref py py-attr docutils literal notranslate"><span class="pre">Process.stdout</span></code> and <code class="xref py py-attr docutils literal notranslate"><span class="pre">Process.stderr</span></code>

  269. (if <a class="reference internal" href="subprocess.html#subprocess.PIPE" title="subprocess.PIPE"><code class="xref py py-const docutils literal notranslate"><span class="pre">subprocess.PIPE</span></code></a> is passed to <em>stdout</em> and <em>stderr</em> arguments).</p>

  270. <p>Return a <a class="reference internal" href="#asyncio.subprocess.Process" title="asyncio.subprocess.Process"><code class="xref py py-class docutils literal notranslate"><span class="pre">Process</span></code></a> instance.</p>

  271. <p>See the documentation of <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.subprocess_shell" title="asyncio.loop.subprocess_shell"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.subprocess_shell()</span></code></a> for other

  272. parameters.</p>

  273. <div class="admonition important">

  274. <p class="admonition-title">Important</p>

  275. <p>It is the application’s responsibility to ensure that all whitespace and

  276. special characters are quoted appropriately to avoid <a class="reference external" href="https://en.wikipedia.org/wiki/Shell_injection#Shell_injection">shell injection</a>

  277. vulnerabilities. The <a class="reference internal" href="shlex.html#shlex.quote" title="shlex.quote"><code class="xref py py-func docutils literal notranslate"><span class="pre">shlex.quote()</span></code></a> function can be used to properly

  278. escape whitespace and special shell characters in strings that are going

  279. to be used to construct shell commands.</p>

  280. </div>

  281. <div class="versionchanged">

  282. <p><span class="versionmodified changed">Changed in version 3.10: </span>Removed the <em>loop</em> parameter.</p>

  283. </div>

  284. </dd></dl>

  285. 

  286. <div class="admonition note">

  287. <p class="admonition-title">Note</p>

  288. <p>Subprocesses are available for Windows if a <a class="reference internal" href="asyncio-eventloop.html#asyncio.ProactorEventLoop" title="asyncio.ProactorEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">ProactorEventLoop</span></code></a> is

  289. used. See <a class="reference internal" href="asyncio-platforms.html#asyncio-windows-subprocess"><span class="std std-ref">Subprocess Support on Windows</span></a>

  290. for details.</p>

  291. </div>

  292. <div class="admonition seealso">

  293. <p class="admonition-title">See also</p>

  294. <p>asyncio also has the following <em>low-level</em> APIs to work with subprocesses:

  295. <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.subprocess_exec" title="asyncio.loop.subprocess_exec"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.subprocess_exec()</span></code></a>, <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.subprocess_shell" title="asyncio.loop.subprocess_shell"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.subprocess_shell()</span></code></a>,

  296. <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.connect_read_pipe" title="asyncio.loop.connect_read_pipe"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.connect_read_pipe()</span></code></a>, <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.connect_write_pipe" title="asyncio.loop.connect_write_pipe"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.connect_write_pipe()</span></code></a>,

  297. as well as the <a class="reference internal" href="asyncio-protocol.html#asyncio-subprocess-transports"><span class="std std-ref">Subprocess Transports</span></a>

  298. and <a class="reference internal" href="asyncio-protocol.html#asyncio-subprocess-protocols"><span class="std std-ref">Subprocess Protocols</span></a>.</p>

  299. </div>

  300. </section>

  301. <section id="constants">

  302. <h2>Constants<a class="headerlink" href="#constants" title="Link to this heading">¶</a></h2>

  303. <dl class="py data">

  304. <dt class="sig sig-object py" id="asyncio.subprocess.PIPE">

  305. <span class="sig-prename descclassname"><span class="pre">asyncio.subprocess.</span></span><span class="sig-name descname"><span class="pre">PIPE</span></span><a class="headerlink" href="#asyncio.subprocess.PIPE" title="Link to this definition">¶</a></dt>

  306. <dd><p>Can be passed to the <em>stdin</em>, <em>stdout</em> or <em>stderr</em> parameters.</p>

  307. <p>If <em>PIPE</em> is passed to <em>stdin</em> argument, the

  308. <a class="reference internal" href="#asyncio.subprocess.Process.stdin" title="asyncio.subprocess.Process.stdin"><code class="xref py py-attr docutils literal notranslate"><span class="pre">Process.stdin</span></code></a> attribute

  309. will point to a <code class="xref py py-class docutils literal notranslate"><span class="pre">StreamWriter</span></code> instance.</p>

  310. <p>If <em>PIPE</em> is passed to <em>stdout</em> or <em>stderr</em> arguments, the

  311. <a class="reference internal" href="#asyncio.subprocess.Process.stdout" title="asyncio.subprocess.Process.stdout"><code class="xref py py-attr docutils literal notranslate"><span class="pre">Process.stdout</span></code></a> and

  312. <a class="reference internal" href="#asyncio.subprocess.Process.stderr" title="asyncio.subprocess.Process.stderr"><code class="xref py py-attr docutils literal notranslate"><span class="pre">Process.stderr</span></code></a>

  313. attributes will point to <code class="xref py py-class docutils literal notranslate"><span class="pre">StreamReader</span></code> instances.</p>

  314. </dd></dl>

  315. 

  316. <dl class="py data">

  317. <dt class="sig sig-object py" id="asyncio.subprocess.STDOUT">

  318. <span class="sig-prename descclassname"><span class="pre">asyncio.subprocess.</span></span><span class="sig-name descname"><span class="pre">STDOUT</span></span><a class="headerlink" href="#asyncio.subprocess.STDOUT" title="Link to this definition">¶</a></dt>

  319. <dd><p>Special value that can be used as the <em>stderr</em> argument and indicates

  320. that standard error should be redirected into standard output.</p>

  321. </dd></dl>

  322. 

  323. <dl class="py data">

  324. <dt class="sig sig-object py" id="asyncio.subprocess.DEVNULL">

  325. <span class="sig-prename descclassname"><span class="pre">asyncio.subprocess.</span></span><span class="sig-name descname"><span class="pre">DEVNULL</span></span><a class="headerlink" href="#asyncio.subprocess.DEVNULL" title="Link to this definition">¶</a></dt>

  326. <dd><p>Special value that can be used as the <em>stdin</em>, <em>stdout</em> or <em>stderr</em> argument

  327. to process creation functions.  It indicates that the special file

  328. <a class="reference internal" href="os.html#os.devnull" title="os.devnull"><code class="xref py py-data docutils literal notranslate"><span class="pre">os.devnull</span></code></a> will be used for the corresponding subprocess stream.</p>

  329. </dd></dl>

  330. 

  331. </section>

  332. <section id="interacting-with-subprocesses">

  333. <h2>Interacting with Subprocesses<a class="headerlink" href="#interacting-with-subprocesses" title="Link to this heading">¶</a></h2>

  334. <p>Both <a class="reference internal" href="#asyncio.create_subprocess_exec" title="asyncio.create_subprocess_exec"><code class="xref py py-func docutils literal notranslate"><span class="pre">create_subprocess_exec()</span></code></a> and <a class="reference internal" href="#asyncio.create_subprocess_shell" title="asyncio.create_subprocess_shell"><code class="xref py py-func docutils literal notranslate"><span class="pre">create_subprocess_shell()</span></code></a>

  335. functions return instances of the <em>Process</em> class.  <em>Process</em> is a high-level

  336. wrapper that allows communicating with subprocesses and watching for

  337. their completion.</p>

  338. <dl class="py class">

  339. <dt class="sig sig-object py" id="asyncio.subprocess.Process">

  340. <em class="property"><span class="pre">class</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">asyncio.subprocess.</span></span><span class="sig-name descname"><span class="pre">Process</span></span><a class="headerlink" href="#asyncio.subprocess.Process" title="Link to this definition">¶</a></dt>

  341. <dd><p>An object that wraps OS processes created by the

  342. <code class="xref py py-func docutils literal notranslate"><span class="pre">create_subprocess_exec()</span></code> and <code class="xref py py-func docutils literal notranslate"><span class="pre">create_subprocess_shell()</span></code>

  343. functions.</p>

  344. <p>This class is designed to have a similar API to the

  345. <a class="reference internal" href="subprocess.html#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">subprocess.Popen</span></code></a> class, but there are some

  346. notable differences:</p>

  347. <ul class="simple">

  348. <li><p>unlike Popen, Process instances do not have an equivalent to

  349. the <a class="reference internal" href="subprocess.html#subprocess.Popen.poll" title="subprocess.Popen.poll"><code class="xref py py-meth docutils literal notranslate"><span class="pre">poll()</span></code></a> method;</p></li>

  350. <li><p>the <a class="reference internal" href="#asyncio.subprocess.Process.communicate" title="asyncio.subprocess.Process.communicate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">communicate()</span></code></a> and

  351. <a class="reference internal" href="#asyncio.subprocess.Process.wait" title="asyncio.subprocess.Process.wait"><code class="xref py py-meth docutils literal notranslate"><span class="pre">wait()</span></code></a> methods don’t have a

  352. <em>timeout</em> parameter: use the <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">wait_for()</span></code></a> function;</p></li>

  353. <li><p>the <a class="reference internal" href="#asyncio.subprocess.Process.wait" title="asyncio.subprocess.Process.wait"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Process.wait()</span></code></a> method

  354. is asynchronous, whereas <a class="reference internal" href="subprocess.html#subprocess.Popen.wait" title="subprocess.Popen.wait"><code class="xref py py-meth docutils literal notranslate"><span class="pre">subprocess.Popen.wait()</span></code></a> method

  355. is implemented as a blocking busy loop;</p></li>

  356. <li><p>the <em>universal_newlines</em> parameter is not supported.</p></li>

  357. </ul>

  358. <p>This class is <a class="reference internal" href="asyncio-dev.html#asyncio-multithreading"><span class="std std-ref">not thread safe</span></a>.</p>

  359. <p>See also the <a class="reference internal" href="#asyncio-subprocess-threads"><span class="std std-ref">Subprocess and Threads</span></a>

  360. section.</p>

  361. <dl class="py method">

  362. <dt class="sig sig-object py" id="asyncio.subprocess.Process.wait">

  363. <em class="property"><span class="pre">coroutine</span> </em><span class="sig-name descname"><span class="pre">wait</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.subprocess.Process.wait" title="Link to this definition">¶</a></dt>

  364. <dd><p>Wait for the child process to terminate.</p>

  365. <p>Set and return the <a class="reference internal" href="#asyncio.subprocess.Process.returncode" title="asyncio.subprocess.Process.returncode"><code class="xref py py-attr docutils literal notranslate"><span class="pre">returncode</span></code></a> attribute.</p>

  366. <div class="admonition note">

  367. <p class="admonition-title">Note</p>

  368. <p>This method can deadlock when using <code class="docutils literal notranslate"><span class="pre">stdout=PIPE</span></code> or

  369. <code class="docutils literal notranslate"><span class="pre">stderr=PIPE</span></code> and the child process generates so much output

  370. that it blocks waiting for the OS pipe buffer to accept

  371. more data. Use the <a class="reference internal" href="#asyncio.subprocess.Process.communicate" title="asyncio.subprocess.Process.communicate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">communicate()</span></code></a> method when using pipes

  372. to avoid this condition.</p>

  373. </div>

  374. </dd></dl>

  375. 

  376. <dl class="py method">

  377. <dt class="sig sig-object py" id="asyncio.subprocess.Process.communicate">

  378. <em class="property"><span class="pre">coroutine</span> </em><span class="sig-name descname"><span class="pre">communicate</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">input</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.subprocess.Process.communicate" title="Link to this definition">¶</a></dt>

  379. <dd><p>Interact with process:</p>

  380. <ol class="arabic simple">

  381. <li><p>send data to <em>stdin</em> (if <em>input</em> is not <code class="docutils literal notranslate"><span class="pre">None</span></code>);</p></li>

  382. <li><p>closes <em>stdin</em>;</p></li>

  383. <li><p>read data from <em>stdout</em> and <em>stderr</em>, until EOF is reached;</p></li>

  384. <li><p>wait for process to terminate.</p></li>

  385. </ol>

  386. <p>The optional <em>input</em> argument is the data (<a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> object)

  387. that will be sent to the child process.</p>

  388. <p>Return a tuple <code class="docutils literal notranslate"><span class="pre">(stdout_data,</span> <span class="pre">stderr_data)</span></code>.</p>

  389. <p>If either <a class="reference internal" href="exceptions.html#BrokenPipeError" title="BrokenPipeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">BrokenPipeError</span></code></a> or <a class="reference internal" href="exceptions.html#ConnectionResetError" title="ConnectionResetError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ConnectionResetError</span></code></a>

  390. exception is raised when writing <em>input</em> into <em>stdin</em>, the

  391. exception is ignored.  This condition occurs when the process

  392. exits before all data are written into <em>stdin</em>.</p>

  393. <p>If it is desired to send data to the process’ <em>stdin</em>,

  394. the process needs to be created with <code class="docutils literal notranslate"><span class="pre">stdin=PIPE</span></code>.  Similarly,

  395. to get anything other than <code class="docutils literal notranslate"><span class="pre">None</span></code> in the result tuple, the

  396. process has to be created with <code class="docutils literal notranslate"><span class="pre">stdout=PIPE</span></code> and/or

  397. <code class="docutils literal notranslate"><span class="pre">stderr=PIPE</span></code> arguments.</p>

  398. <p>Note, that the data read is buffered in memory, so do not use

  399. this method if the data size is large or unlimited.</p>

  400. <div class="versionchanged">

  401. <p><span class="versionmodified changed">Changed in version 3.12: </span><em>stdin</em> gets closed when <cite>input=None</cite> too.</p>

  402. </div>

  403. </dd></dl>

  404. 

  405. <dl class="py method">

  406. <dt class="sig sig-object py" id="asyncio.subprocess.Process.send_signal">

  407. <span class="sig-name descname"><span class="pre">send_signal</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">signal</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.subprocess.Process.send_signal" title="Link to this definition">¶</a></dt>

  408. <dd><p>Sends the signal <em>signal</em> to the child process.</p>

  409. <div class="admonition note">

  410. <p class="admonition-title">Note</p>

  411. <p>On Windows, <a class="reference internal" href="signal.html#signal.SIGTERM" title="signal.SIGTERM"><code class="xref py py-const docutils literal notranslate"><span class="pre">SIGTERM</span></code></a> is an alias for <a class="reference internal" href="#asyncio.subprocess.Process.terminate" title="asyncio.subprocess.Process.terminate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">terminate()</span></code></a>.

  412. <code class="docutils literal notranslate"><span class="pre">CTRL_C_EVENT</span></code> and <code class="docutils literal notranslate"><span class="pre">CTRL_BREAK_EVENT</span></code> can be sent to processes

  413. started with a <em>creationflags</em> parameter which includes

  414. <code class="docutils literal notranslate"><span class="pre">CREATE_NEW_PROCESS_GROUP</span></code>.</p>

  415. </div>

  416. </dd></dl>

  417. 

  418. <dl class="py method">

  419. <dt class="sig sig-object py" id="asyncio.subprocess.Process.terminate">

  420. <span class="sig-name descname"><span class="pre">terminate</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.subprocess.Process.terminate" title="Link to this definition">¶</a></dt>

  421. <dd><p>Stop the child process.</p>

  422. <p>On POSIX systems this method sends <a class="reference internal" href="signal.html#signal.SIGTERM" title="signal.SIGTERM"><code class="xref py py-const docutils literal notranslate"><span class="pre">SIGTERM</span></code></a> to the

  423. child process.</p>

  424. <p>On Windows the Win32 API function <code class="xref c c-func docutils literal notranslate"><span class="pre">TerminateProcess()</span></code> is

  425. called to stop the child process.</p>

  426. </dd></dl>

  427. 

  428. <dl class="py method">

  429. <dt class="sig sig-object py" id="asyncio.subprocess.Process.kill">

  430. <span class="sig-name descname"><span class="pre">kill</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.subprocess.Process.kill" title="Link to this definition">¶</a></dt>

  431. <dd><p>Kill the child process.</p>

  432. <p>On POSIX systems this method sends <code class="xref py py-data docutils literal notranslate"><span class="pre">SIGKILL</span></code> to the child

  433. process.</p>

  434. <p>On Windows this method is an alias for <a class="reference internal" href="#asyncio.subprocess.Process.terminate" title="asyncio.subprocess.Process.terminate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">terminate()</span></code></a>.</p>

  435. </dd></dl>

  436. 

  437. <dl class="py attribute">

  438. <dt class="sig sig-object py" id="asyncio.subprocess.Process.stdin">

  439. <span class="sig-name descname"><span class="pre">stdin</span></span><a class="headerlink" href="#asyncio.subprocess.Process.stdin" title="Link to this definition">¶</a></dt>

  440. <dd><p>Standard input stream (<code class="xref py py-class docutils literal notranslate"><span class="pre">StreamWriter</span></code>) or <code class="docutils literal notranslate"><span class="pre">None</span></code>

  441. if the process was created with <code class="docutils literal notranslate"><span class="pre">stdin=None</span></code>.</p>

  442. </dd></dl>

  443. 

  444. <dl class="py attribute">

  445. <dt class="sig sig-object py" id="asyncio.subprocess.Process.stdout">

  446. <span class="sig-name descname"><span class="pre">stdout</span></span><a class="headerlink" href="#asyncio.subprocess.Process.stdout" title="Link to this definition">¶</a></dt>

  447. <dd><p>Standard output stream (<code class="xref py py-class docutils literal notranslate"><span class="pre">StreamReader</span></code>) or <code class="docutils literal notranslate"><span class="pre">None</span></code>

  448. if the process was created with <code class="docutils literal notranslate"><span class="pre">stdout=None</span></code>.</p>

  449. </dd></dl>

  450. 

  451. <dl class="py attribute">

  452. <dt class="sig sig-object py" id="asyncio.subprocess.Process.stderr">

  453. <span class="sig-name descname"><span class="pre">stderr</span></span><a class="headerlink" href="#asyncio.subprocess.Process.stderr" title="Link to this definition">¶</a></dt>

  454. <dd><p>Standard error stream (<code class="xref py py-class docutils literal notranslate"><span class="pre">StreamReader</span></code>) or <code class="docutils literal notranslate"><span class="pre">None</span></code>

  455. if the process was created with <code class="docutils literal notranslate"><span class="pre">stderr=None</span></code>.</p>

  456. </dd></dl>

  457. 

  458. <div class="admonition warning">

  459. <p class="admonition-title">Warning</p>

  460. <p>Use the <a class="reference internal" href="#asyncio.subprocess.Process.communicate" title="asyncio.subprocess.Process.communicate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">communicate()</span></code></a> method rather than

  461. <a class="reference internal" href="#asyncio.subprocess.Process.stdin" title="asyncio.subprocess.Process.stdin"><code class="xref py py-attr docutils literal notranslate"><span class="pre">process.stdin.write()</span></code></a>,

  462. <a class="reference internal" href="#asyncio.subprocess.Process.stdout" title="asyncio.subprocess.Process.stdout"><code class="xref py py-attr docutils literal notranslate"><span class="pre">await</span> <span class="pre">process.stdout.read()</span></code></a> or

  463. <a class="reference internal" href="#asyncio.subprocess.Process.stderr" title="asyncio.subprocess.Process.stderr"><code class="xref py py-attr docutils literal notranslate"><span class="pre">await</span> <span class="pre">process.stderr.read()</span></code></a>.

  464. This avoids deadlocks due to streams pausing reading or writing

  465. and blocking the child process.</p>

  466. </div>

  467. <dl class="py attribute">

  468. <dt class="sig sig-object py" id="asyncio.subprocess.Process.pid">

  469. <span class="sig-name descname"><span class="pre">pid</span></span><a class="headerlink" href="#asyncio.subprocess.Process.pid" title="Link to this definition">¶</a></dt>

  470. <dd><p>Process identification number (PID).</p>

  471. <p>Note that for processes created by the <code class="xref py py-func docutils literal notranslate"><span class="pre">create_subprocess_shell()</span></code>

  472. function, this attribute is the PID of the spawned shell.</p>

  473. </dd></dl>

  474. 

  475. <dl class="py attribute">

  476. <dt class="sig sig-object py" id="asyncio.subprocess.Process.returncode">

  477. <span class="sig-name descname"><span class="pre">returncode</span></span><a class="headerlink" href="#asyncio.subprocess.Process.returncode" title="Link to this definition">¶</a></dt>

  478. <dd><p>Return code of the process when it exits.</p>

  479. <p>A <code class="docutils literal notranslate"><span class="pre">None</span></code> value indicates that the process has not terminated yet.</p>

  480. <p>A negative value <code class="docutils literal notranslate"><span class="pre">-N</span></code> indicates that the child was terminated

  481. by signal <code class="docutils literal notranslate"><span class="pre">N</span></code> (POSIX only).</p>

  482. </dd></dl>

  483. 

  484. </dd></dl>

  485. 

  486. <section id="subprocess-and-threads">

  487. <span id="asyncio-subprocess-threads"></span><h3>Subprocess and Threads<a class="headerlink" href="#subprocess-and-threads" title="Link to this heading">¶</a></h3>

  488. <p>Standard asyncio event loop supports running subprocesses from different threads by

  489. default.</p>

  490. <p>On Windows subprocesses are provided by <a class="reference internal" href="asyncio-eventloop.html#asyncio.ProactorEventLoop" title="asyncio.ProactorEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">ProactorEventLoop</span></code></a> only (default),

  491. <a class="reference internal" href="asyncio-eventloop.html#asyncio.SelectorEventLoop" title="asyncio.SelectorEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">SelectorEventLoop</span></code></a> has no subprocess support.</p>

  492. <p>On UNIX <em>child watchers</em> are used for subprocess finish waiting, see

  493. <a class="reference internal" href="asyncio-policy.html#asyncio-watchers"><span class="std std-ref">Process Watchers</span></a> for more info.</p>

  494. <div class="versionchanged">

  495. <p><span class="versionmodified changed">Changed in version 3.8: </span>UNIX switched to use <a class="reference internal" href="asyncio-policy.html#asyncio.ThreadedChildWatcher" title="asyncio.ThreadedChildWatcher"><code class="xref py py-class docutils literal notranslate"><span class="pre">ThreadedChildWatcher</span></code></a> for spawning subprocesses from

  496. different threads without any limitation.</p>

  497. <p>Spawning a subprocess with <em>inactive</em> current child watcher raises

  498. <a class="reference internal" href="exceptions.html#RuntimeError" title="RuntimeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">RuntimeError</span></code></a>.</p>

  499. </div>

  500. <p>Note that alternative event loop implementations might have own limitations;

  501. please refer to their documentation.</p>

  502. <div class="admonition seealso">

  503. <p class="admonition-title">See also</p>

  504. <p>The <a class="reference internal" href="asyncio-dev.html#asyncio-multithreading"><span class="std std-ref">Concurrency and multithreading in asyncio</span></a> section.</p>

  505. </div>

  506. </section>

  507. <section id="examples">

  508. <h3>Examples<a class="headerlink" href="#examples" title="Link to this heading">¶</a></h3>

  509. <p>An example using the <a class="reference internal" href="#asyncio.subprocess.Process" title="asyncio.subprocess.Process"><code class="xref py py-class docutils literal notranslate"><span class="pre">Process</span></code></a> class to

  510. control a subprocess and the <a class="reference internal" href="asyncio-stream.html#asyncio.StreamReader" title="asyncio.StreamReader"><code class="xref py py-class docutils literal notranslate"><span class="pre">StreamReader</span></code></a> class to read from

  511. its standard output.</p>

  512. <p id="asyncio-example-create-subprocess-exec">The subprocess is created by the <a class="reference internal" href="#asyncio.create_subprocess_exec" title="asyncio.create_subprocess_exec"><code class="xref py py-func docutils literal notranslate"><span class="pre">create_subprocess_exec()</span></code></a>

  513. function:</p>

  514. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">asyncio</span>

  515. <span class="kn">import</span> <span class="nn">sys</span>

  516. 

  517. <span class="k">async</span> <span class="k">def</span> <span class="nf">get_date</span><span class="p">():</span>

  518.     <span class="n">code</span> <span class="o">=</span> <span class="s1">&#39;import datetime; print(datetime.datetime.now())&#39;</span>

  519. 

  520.     <span class="c1"># Create the subprocess; redirect the standard output</span>

  521.     <span class="c1"># into a pipe.</span>

  522.     <span class="n">proc</span> <span class="o">=</span> <span class="k">await</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">create_subprocess_exec</span><span class="p">(</span>

  523.         <span class="n">sys</span><span class="o">.</span><span class="n">executable</span><span class="p">,</span> <span class="s1">&#39;-c&#39;</span><span class="p">,</span> <span class="n">code</span><span class="p">,</span>

  524.         <span class="n">stdout</span><span class="o">=</span><span class="n">asyncio</span><span class="o">.</span><span class="n">subprocess</span><span class="o">.</span><span class="n">PIPE</span><span class="p">)</span>

  525. 

  526.     <span class="c1"># Read one line of output.</span>

  527.     <span class="n">data</span> <span class="o">=</span> <span class="k">await</span> <span class="n">proc</span><span class="o">.</span><span class="n">stdout</span><span class="o">.</span><span class="n">readline</span><span class="p">()</span>

  528.     <span class="n">line</span> <span class="o">=</span> <span class="n">data</span><span class="o">.</span><span class="n">decode</span><span class="p">(</span><span class="s1">&#39;ascii&#39;</span><span class="p">)</span><span class="o">.</span><span class="n">rstrip</span><span class="p">()</span>

  529. 

  530.     <span class="c1"># Wait for the subprocess exit.</span>

  531.     <span class="k">await</span> <span class="n">proc</span><span class="o">.</span><span class="n">wait</span><span class="p">()</span>

  532.     <span class="k">return</span> <span class="n">line</span>

  533. 

  534. <span class="n">date</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">get_date</span><span class="p">())</span>

  535. <span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">&quot;Current date: </span><span class="si">{</span><span class="n">date</span><span class="si">}</span><span class="s2">&quot;</span><span class="p">)</span>

  536. </pre></div>

  537. </div>

  538. <p>See also the <a class="reference internal" href="asyncio-protocol.html#asyncio-example-subprocess-proto"><span class="std std-ref">same example</span></a>

  539. written using low-level APIs.</p>

  540. </section>

  541. </section>

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