blocks|key|2932429|text|有两种方法可以进行重定向。两者都适用于subprocess.Popen或subprocess.call。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2932430|2932431|设置关键字参数shell+=+True或executable+=+/path/to/the/shell，并按原样指定命令。|ordered-list-item|2932432|由于您只是将输出重定向到文件，因此请设置关键字参数|2932433|2932434|标准输出=+an_open_writeable_file_object|2932435|对象指向output文件的位置。|2932436|subprocess.Popen比subprocess.call更通用。|2932437|Popen不会阻塞，允许您在进程运行时与其交互，或者继续执行您的Python程序中的其他操作。对Popen的调用返回一个Popen对象。|2932438|call确实阻塞了。虽然它支持所有与Popen构造函数相同的参数，因此您仍然可以设置进程的输出、环境变量等，但您的脚本等待程序完成，并且call返回一个表示进程退出状态的代码。|2932439|returncode+=+call(*args,+**kwargs)+|code-block|syntax|javascript|2932440|基本上等同于调用|2932441|returncode+=+Popen(*args,+**kwargs).wait()|2932442|call只是一个方便的函数。它的CPython实现是用subprocess.py实现的|2932443|def+call(*popenargs,+timeout=None,+**kwargs):
++++"""Run+command+with+arguments.++Wait+for+command+to+complete+or
++++timeout,+then+return+the+returncode+attribute.

++++The+arguments+are+the+same+as+for+the+Popen+constructor.++Example:

++++retcode+=+call(["ls",+"-l"])
++++"""
++++with+Popen(*popenargs,+**kwargs)+as+p:
++++++++try:
++++++++++++return+p.wait(timeout=timeout)
++++++++except:
++++++++++++p.kill()
++++++++++++p.wait()
++++++++++++raise|2932444|如您所见，它只是对Popen进行了简单的包装。|2932445|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.python.org/library/subprocess.html#subprocess.Popen|1|http://docs.python.org/library/subprocess.html#subprocess.call|2|http://hg.python.org/cpython/file/e0df7db13d55/Lib/subprocess.py#l459^0|J|G|10|F|0|0|7|C|K|V|0|0|0|0|4|6|0|0|G|H|F|0|G|0|H|F|1|0|0|5|1C|5|1O|5|0|0|4|I|5|1W|4|0|0|0|0|0|4|R|D|2|0|0|9|5|0^^$0|@$1|2|3|4|5|6|7|1N|8|@$9|1O|A|1P|B|C]|$9|1Q|A|1R|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|1S|8|@]|D|@]|E|$]]|$1|G|3|H|5|I|7|1T|8|@$9|1U|A|1V|B|C]|$9|1W|A|1X|B|C]]|D|@]|E|$]]|$1|J|3|K|5|I|7|1Y|8|@]|D|@]|E|$]]|$1|L|3|-4|5|6|7|1Z|8|@]|D|@]|E|$]]|$1|M|3|N|5|6|7|20|8|@]|D|@]|E|$]]|$1|O|3|P|5|6|7|21|8|@$9|22|A|23|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|6|7|24|8|@$9|25|A|26|B|C]|$9|27|A|28|B|C]]|D|@$9|29|A|2A|1|2B]|$9|2C|A|2D|1|2E]]|E|$]]|$1|S|3|T|5|6|7|2F|8|@$9|2G|A|2H|B|C]|$9|2I|A|2J|B|C]|$9|2K|A|2L|B|C]]|D|@]|E|$]]|$1|U|3|V|5|6|7|2M|8|@$9|2N|A|2O|B|C]|$9|2P|A|2Q|B|C]|$9|2R|A|2S|B|C]]|D|@]|E|$]]|$1|W|3|X|5|Y|7|2T|8|@]|D|@]|E|$Z|10]]|$1|11|3|12|5|6|7|2U|8|@]|D|@]|E|$]]|$1|13|3|14|5|Y|7|2V|8|@]|D|@]|E|$Z|10]]|$1|15|3|16|5|6|7|2W|8|@$9|2X|A|2Y|B|C]]|D|@$9|2Z|A|30|1|31]]|E|$]]|$1|17|3|18|5|Y|7|32|8|@]|D|@]|E|$Z|10]]|$1|19|3|1A|5|6|7|33|8|@$9|34|A|35|B|C]]|D|@]|E|$]]|$1|1B|3|-4|5|6|7|36|8|@]|D|@]|E|$]]]|1C|$1D|$5|1E|1F|1G|E|$1H|1I]]|1J|$5|1E|1F|1G|E|$1H|1K]]|1L|$5|1E|1F|1G|E|$1H|1M]]]]

There are two ways to do the redirect. Both apply to either <code>subprocess.Popen</code> or <code>subprocess.call</code>.

<ol>
<li>Set the keyword argument <code>shell = True</code> or <code>executable = /path/to/the/shell</code> and specify the command just as you have it there.</li>
<li>Since you're just redirecting the output to a file, set the keyword argument

<pre><code>stdout = an_open_writeable_file_object
</code></pre>

where the object points to the <code>output</code> file.</li>
</ol>

<a href="http://docs.python.org/library/subprocess.html#subprocess.Popen" rel="noreferrer"><code>subprocess.Popen</code></a> is more general than <a href="http://docs.python.org/library/subprocess.html#subprocess.call" rel="noreferrer"><code>subprocess.call</code></a>.

<code>Popen</code> doesn't block, allowing you to interact with the process while it's running, or continue with other things in your Python program. The call to <code>Popen</code> returns a <code>Popen</code> object.

<code>call</code> does block. While it supports all the same arguments as the <code>Popen</code> constructor, so you can still set the process' output, environmental variables, etc., your script waits for the program to complete, and <code>call</code> returns a code representing the process' exit status. 

<pre><code>returncode = call(*args, **kwargs) 
</code></pre>

is basically the same as calling 

<pre><code>returncode = Popen(*args, **kwargs).wait()
</code></pre>

<code>call</code> is just a convenience function. It's implementation in CPython is in <a href="http://hg.python.org/cpython/file/e0df7db13d55/Lib/subprocess.py#l459" rel="noreferrer">subprocess.py</a>:

<pre><code>def call(*popenargs, timeout=None, **kwargs):
 """Run command with arguments. Wait for command to complete or
 timeout, then return the returncode attribute.

 The arguments are the same as for the Popen constructor. Example:

 retcode = call(["ls", "-l"])
 """
 with Popen(*popenargs, **kwargs) as p:
 try:
 return p.wait(timeout=timeout)
 except:
 p.kill()
 p.wait()
 raise
</code></pre>

As you can see, it's a thin wrapper around <code>Popen</code>.

blocks|key|2932453|text|另一个答案非常完整，但这里有一个经验法则：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2932454|2932455|call阻塞：|unordered-list-item|offset|length|style|CODE|2932456|2932457|closed|2932458|Popen+(‘notepad.exe’)+print('hello')+#仅当notepad为非阻塞时才执行：|2932459|2932460|Popen('notepad.exe')+print('hello')+#立即执行|2932461|entityMap^0|0|0|0|4|0|0|0|0|5|0|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|U|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|V|8|@$F|W|G|X|H|I]]|9|@]|A|$]]|$1|J|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|Z|8|@]|9|@]|A|$]]|$1|M|3|N|5|E|7|10|8|@$F|11|G|12|H|I]]|9|@]|A|$]]|$1|O|3|-4|5|6|7|13|8|@]|9|@]|A|$]]|$1|P|3|Q|5|6|7|14|8|@]|9|@]|A|$]]|$1|R|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|S|$]]

The other answer is very complete, but here is a rule of thumb:

<ul>
<li><code>call</code> is blocking:

<pre><code>call('notepad.exe')
print('hello') # only executed when notepad is closed
</code></pre></li>
<li><code>Popen</code> is non-blocking:

<pre><code>Popen('notepad.exe')
print('hello') # immediately executed
</code></pre></li>
</ul>

I want to call an external program from Python. I have used both <code>Popen()</code> and <code>call()</code> to do that. 

What's the difference between the two?

My specific goal is to run the following command from Python. I am not sure how redirects work.

<pre><code>./my_script.sh &gt; output
</code></pre>

I read <a href="http://docs.python.org/library/subprocess.html" rel="noreferrer">the documentation</a> and it says that <code>call()</code> is a convenience function or a shortcut function. Do we lose any power by using <code>call()</code> instead of <code>Popen()</code>?

What's the difference between subprocess Popen and call (how can I use them)?

我想从Python调用一个外部程序。我已经使用了Popen()和call()来做到这一点。这两者有什么不同？我的具体目标是从Python运行以下命令。我不确定重定向是如何工作的。./my_script.sh > output我读过，上面说call()是一个方便函数或快捷函数。我们是否会因为使用call()而不使用Pop...

问子进程Popen和call有什么不同(我如何使用它们)？
EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问子进程Popen和call有什么不同(我如何使用它们)？EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问子进程Popen和call有什么不同(我如何使用它们)？
EN