blocks|key|1240700|text|output+=+os.popen('cat+/tmp/baz').read()|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1240701|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>output = os.popen('cat /tmp/baz').read()
</code></pre>

blocks|key|1455543|text|最灵活的方法是使用subprocess模块：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1455544|import+subprocess

out+=+subprocess.run(["cat",+"/tmp/baz"],+capture_output=True)
print("program+output:",+out)|code-block|syntax|javascript|1455545|capture_output是在Python3.7中引入的，对于较老的版本，可以使用特殊的函数check_output()：|1455546|out+=+subprocess.check_output(["cat",+"/tmp/baz"])|1455547|如果您需要细粒度控制，也可以手动构造子流程对象：|1455548|proc+=+subprocess.Popen(["cat",+"/tmp/baz"],+stdout=subprocess.PIPE)
(out,+err)+=+proc.communicate()|1455549|所有这些函数都支持keyword+parameters自定义子流程的执行方式。例如，如果您需要*的文件名扩展之类的东西，您可以使用shell=True通过shell执行程序，但这是limitations附带的。|1455550|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.python.org/library/subprocess.html|1|https://docs.python.org/3/library/subprocess.html#frequently-used-arguments|2|https://docs.python.org/3/library/subprocess.html#security-considerations^0|9|A|9|A|0|0|0|0|E|1B|E|0|0|0|0|1B|1|1T|A|9|I|1|2I|B|2|0^^$0|@$1|2|3|4|5|6|7|16|8|@$9|17|A|18|B|C]]|D|@$9|19|A|1A|1|1B]]|E|$]]|$1|F|3|G|5|H|7|1C|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1D|8|@$9|1E|A|1F|B|C]|$9|1G|A|1H|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|1I|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|1J|8|@]|D|@]|E|$]]|$1|Q|3|R|5|H|7|1K|8|@]|D|@]|E|$I|J]]|$1|S|3|T|5|6|7|1L|8|@$9|1M|A|1N|B|C]|$9|1O|A|1P|B|C]]|D|@$9|1Q|A|1R|1|1S]|$9|1T|A|1U|1|1V]]|E|$]]|$1|U|3|-4|5|6|7|1W|8|@]|D|@]|E|$]]]|V|$W|$5|X|Y|Z|E|$10|11]]|12|$5|X|Y|Z|E|$10|13]]|14|$5|X|Y|Z|E|$10|15]]]]

The most flexible way is to use the <a href="http://docs.python.org/library/subprocess.html" rel="noreferrer"><code>subprocess</code></a> module:

<pre><code>import subprocess

out = subprocess.run(["cat", "/tmp/baz"], capture_output=True)
print("program output:", out)
</code></pre>

<code>capture_output</code> was introduced in Python 3.7, for older versions the special function <code>check_output()</code> can be used instead:

<pre><code>out = subprocess.check_output(["cat", "/tmp/baz"])
</code></pre>

You can also manually construct a subprocess object if you need fine grained control:

<pre><code>proc = subprocess.Popen(["cat", "/tmp/baz"], stdout=subprocess.PIPE)
(out, err) = proc.communicate()
</code></pre>

All these functions support <a href="https://docs.python.org/3/library/subprocess.html#frequently-used-arguments" rel="noreferrer">keyword parameters</a> to customize how exactly the subprocess is executed. You can for example use <code>shell=True</code> to execute the program through the shell, if you need things like file name expansions of <code>*</code>, but that comes with <a href="https://docs.python.org/3/library/subprocess.html#security-considerations" rel="noreferrer">limitations</a>.

blocks|key|1240761|text|foo+=+subprocess.check_output(["cat",+"/tmp/baz"])|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1240762|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>foo = subprocess.check_output(["cat", "/tmp/baz"])
</code></pre>

blocks|key|1455735|text|从Python3.5开始，推荐的方式是使用subprocess.run。从Python+3.7开始，要获得与您所描述的相同的行为，您可以使用：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1455736|cpe+=+subprocess.run("ls",+shell=True,+capture_output=True)|code-block|syntax|javascript|1455737|这将返回一个subprocess.CompletedProcess对象。到标准输出的输出将是cpe.stdout，到标准错误的输出将是cpe.stderr，这两个输出都是bytes对象。您可以使用cpe.stdout.decode()对输出进行解码以获取str对象，也可以通过将text=True传递给subprocess.run来获取|1455738|cpe+=+subprocess.run("ls",+shell=True,+capture_output=True,+text=True)|1455739|在后一种情况下，cpe.stdout和cpe.stderr都是str对象。|1455740|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.python.org/3/library/subprocess.html#subprocess.run^0|L|E|L|E|0|0|0|6|R|1A|A|1V|A|2D|5|2Q|J|3J|3|3V|9|47|E|0|0|8|A|J|A|V|3|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]]|D|@$9|11|A|12|1|13]]|E|$]]|$1|F|3|G|5|H|7|14|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|15|8|@$9|16|A|17|B|C]|$9|18|A|19|B|C]|$9|1A|A|1B|B|C]|$9|1C|A|1D|B|C]|$9|1E|A|1F|B|C]|$9|1G|A|1H|B|C]|$9|1I|A|1J|B|C]|$9|1K|A|1L|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|1M|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|1N|8|@$9|1O|A|1P|B|C]|$9|1Q|A|1R|B|C]|$9|1S|A|1T|B|C]]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|1U|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]]]

From Python 3.5 onward, the recommended way is to use <a href="https://docs.python.org/3/library/subprocess.html#subprocess.run" rel="nofollow noreferrer"><code>subprocess.run</code></a>. Since Python 3.7, to get the same behaviour as you describe, you would use:
<pre><code>cpe = subprocess.run(&quot;ls&quot;, shell=True, capture_output=True)
</code></pre>
This will return a <code>subprocess.CompletedProcess</code> object. The output to stdout will be in <code>cpe.stdout</code>, the output to stderr will be in <code>cpe.stderr</code>, which will both be <code>bytes</code> objects. You can decode the output to get a <code>str</code> object by using <code>cpe.stdout.decode()</code> or get a by passing <code>text=True</code> to <code>subprocess.run</code>:
<pre><code>cpe = subprocess.run(&quot;ls&quot;, shell=True, capture_output=True, text=True)
</code></pre>
In the latter case, <code>cpe.stdout</code> and <code>cpe.stderr</code> are both <code>str</code> objects.

blocks|key|1240714|text|import+os
foo+=+os.popen('cat+/tmp/baz',+'r').read()|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1240715|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>import os
foo = os.popen('cat /tmp/baz', 'r').read()
</code></pre>

blocks|key|1240741|text|如果使用subprocess.Popen，请记住指定bufsize。默认值为0，表示“无缓冲”，而不是“选择合理的默认值”。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1240742|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

If you use subprocess.Popen, remember to specify bufsize. The default is 0, which means "unbuffered", not "choose a reasonable default".

blocks|key|1455670|text|这在python3中不起作用，但在python2中，您可以使用一个自定义的__repr__方法来扩展str，该方法调用您的__repr__命令并返回它，如下所示：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1455671|#!/usr/bin/env+python

import+os

class+Command(str):
++++"""Call+system+commands"""

++++def+__repr__(cmd):
++++++++return+os.popen(cmd).read()|code-block|syntax|javascript|1455672|你可以像这样使用它|1455673|#!/usr/bin/env+python
from+command+import+Command

who_i_am+=+`Command('whoami')`

#+Or+predeclare+your+shell+command+strings
whoami+=+Command('whoami')
who_i_am+=+`whoami`|1455674|entityMap^0|11|8|1E|3|1P|8|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|10|8|@]|D|@]|E|$]]]|P|$]]

This will not work in python3, but in python2 you can extend <code>str</code> with a custom <code>__repr__</code> method that calls your shell command and returns it like so:

<pre><code>#!/usr/bin/env python

import os

class Command(str):
 """Call system commands"""

 def __repr__(cmd):
 return os.popen(cmd).read()
</code></pre>

Which you can use like

<pre><code>#!/usr/bin/env python
from command import Command

who_i_am = `Command('whoami')`

# Or predeclare your shell command strings
whoami = Command('whoami')
who_i_am = `whoami`
</code></pre>

What is the equivalent of the backticks found in Ruby and Perl in Python? That is, in Ruby I can do this:

<pre><code>foo = `cat /tmp/baz`
</code></pre>

What does the equivalent statement look like in Python? I've tried <code>os.system("cat /tmp/baz")</code> but that puts the result to standard out and returns to me the error code of that operation.

Equivalent of Bash Backticks in Python

Python

Perl

在Python中，Ruby和Perl中的反引号对应的是什么？也就是说，在Ruby中我可以这样做：foo = `cat /tmp/baz`在Python中等价的语句是什么样子的？我尝试过os.system("cat /tmp/baz")，但它将结果标准化，并返回给我该操作的错误代码。

问Python中的Bash Backticks等效项
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回答 7

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