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copied!<p>There could be two problems why you are not getting any output in stdout:</p> <ol> <li>The process is dumping all it's output to stderr.</li> <li>The system does not know how to execute <code>"imp -help"</code>.</li> </ol> <p>The solution for the first problem is easy: capture stderr using the argument <code>stderr = subprocess.PIPE</code>.</p> <p>The solution to the second is also easy, but the explanation is a bit longer: Subprocess does not guess much, it will just try to execute the whole string as one command. That means, in your case, it will try to execute <code>"imp -help"</code> as one command. It does not try to execute the command <code>"imp"</code> with the argument <code>"-help"</code>. You have to explicitly tell subprocess the command and the arguments separately.</p> <p>From the python <a href="http://docs.python.org/library/subprocess.html" rel="nofollow">documentation</a> on subprocess:</p> <blockquote> <p>args should be a string, or a sequence of program arguments. The program to execute is normally the first item in the args sequence or the string if a string is given, ...</p> </blockquote> <p>That means you have to separate the command and the arguments and pack them together in a sequence. This: <code>"imp -help"</code> should look like this: <code>["imp", "-help"]</code>. Read the <a href="http://docs.python.org/library/subprocess.html" rel="nofollow">documentation</a> on subprocess for more details on the intricacies of spliting the command and arguments.</p> <p>Here is how the code should look like:</p> <pre><code>import subprocess p=subprocess.Popen(["imp", "-help"], stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE) out,err=p.communicate() </code></pre> <p>Note: you also typed <code>p.communicate</code> instead of <code>p.communicate()</code>. I assume that was a typo in your question, not in your code.</p>

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