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<H2><A NAME="SECTION008820000000000000000">
6.8.2 Popen Objects</A>
</H2>

<P>
Instances of the <tt class="class">Popen</tt> class have the following methods:

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1835' xml:id='l2h-1835' class="method">poll</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Check if child process has terminated.  Returns returncode
attribute.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1836' xml:id='l2h-1836' class="method">wait</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Wait for child process to terminate.  Returns returncode attribute.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1837' xml:id='l2h-1837' class="method">communicate</tt></b>(</nobr></td>
  <td><var>input=None</var>)</td></tr></table></dt>
<dd>
Interact with process: Send data to stdin.  Read data from stdout and
stderr, until end-of-file is reached.  Wait for process to terminate.
The optional <var>input</var> argument should be a string to be sent to the
child process, or <code>None</code>, if no data should be sent to the child.

<P>
communicate() returns a tuple (stdout, stderr).

<P>
<span class="note"><b class="label">Note:</b>
The data read is buffered in memory, so do not use this method
if the data size is large or unlimited.</span>
</dl>

<P>
The following attributes are also available:

<P>
<dl><dt><b><tt id='l2h-1838' xml:id='l2h-1838' class="member">stdin</tt></b></dt>
<dd>
If the <var>stdin</var> argument is <code>PIPE</code>, this attribute is a file
object that provides input to the child process.  Otherwise, it is
<code>None</code>.
</dl>

<P>
<dl><dt><b><tt id='l2h-1839' xml:id='l2h-1839' class="member">stdout</tt></b></dt>
<dd>
If the <var>stdout</var> argument is <code>PIPE</code>, this attribute is a file
object that provides output from the child process.  Otherwise, it is
<code>None</code>.
</dl>

<P>
<dl><dt><b><tt id='l2h-1840' xml:id='l2h-1840' class="member">stderr</tt></b></dt>
<dd>
If the <var>stderr</var> argument is <code>PIPE</code>, this attribute is file
object that provides error output from the child process.  Otherwise,
it is <code>None</code>.
</dl>

<P>
<dl><dt><b><tt id='l2h-1841' xml:id='l2h-1841' class="member">pid</tt></b></dt>
<dd>
The process ID of the child process.
</dl>

<P>
<dl><dt><b><tt id='l2h-1842' xml:id='l2h-1842' class="member">returncode</tt></b></dt>
<dd>
The child return code.  A <code>None</code> value indicates that the process
hasn't terminated yet.  A negative value -N indicates that the child
was terminated by signal N (<span class="Unix">Unix</span> only).
</dl>

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<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
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