6.8.2 Popen Objects

Instances of the Popen class have the following methods:

poll( ): Check if child process has terminated. Returns returncode attribute.

wait( ): Wait for child process to terminate. Returns returncode attribute.

communicate( input=None)

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 input argument should be a string to be sent to the child process, or None, if no data should be sent to the child.

communicate() returns a tuple (stdout, stderr).

Note: The data read is buffered in memory, so do not use this method if the data size is large or unlimited.

The following attributes are also available:

stdin: If the stdin argument is PIPE, this attribute is a file object that provides input to the child process. Otherwise, it is None.

stdout: If the stdout argument is PIPE, this attribute is a file object that provides output from the child process. Otherwise, it is None.

stderr: If the stderr argument is PIPE, this attribute is file object that provides error output from the child process. Otherwise, it is None.

pid: The process ID of the child process.

returncode: The child return code. A None value indicates that the process hasn't terminated yet. A negative value -N indicates that the child was terminated by signal N (Unix only).

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