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copied!<p><a href="https://docs.python.org/3/library/subprocess.html?highlight=subprocess#subprocess.Popen.communicate" rel="noreferrer"><code>Popen.communicate()</code></a> documentation:</p> <blockquote> <p>Note that if you want to send data to the process’s stdin, you need to create the Popen object with stdin=PIPE. Similarly, to get anything other than None in the result tuple, you need to give stdout=PIPE and/or stderr=PIPE too.</p> <p><strong>Replacing os.popen*</strong></p> </blockquote> <pre><code> pipe = os.popen(cmd, 'w', bufsize) # ==> pipe = Popen(cmd, shell=True, bufsize=bufsize, stdin=PIPE).stdin </code></pre> <blockquote> <p><strong>Warning</strong> Use communicate() rather than stdin.write(), stdout.read() or stderr.read() to avoid deadlocks due to any of the other OS pipe buffers filling up and blocking the child process.</p> </blockquote> <p>So your example could be written as follows:</p> <pre><code>from subprocess import Popen, PIPE, STDOUT p = Popen(['grep', 'f'], stdout=PIPE, stdin=PIPE, stderr=STDOUT) grep_stdout = p.communicate(input=b'one\ntwo\nthree\nfour\nfive\nsix\n')[0] print(grep_stdout.decode()) # -> four # -> five # -> </code></pre> <hr> <p>On the current Python 3 version, you could use <a href="https://docs.python.org/3/library/subprocess.html#subprocess.run" rel="noreferrer"><code>subprocess.run</code></a>, to pass input as a string to an external command and get its exit status, and its output as a string back in one call:</p> <pre><code>#!/usr/bin/env python3 from subprocess import run, PIPE p = run(['grep', 'f'], stdout=PIPE, input='one\ntwo\nthree\nfour\nfive\nsix\n', encoding='ascii') print(p.returncode) # -> 0 print(p.stdout) # -> four # -> five # -> </code></pre>

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