[Python-Dev] A question about the subprocess implementation (original) (raw)

Phil Vandry vandry at TZoNE.ORG
Sun Jan 8 03:28:56 CET 2012

On 2012-01-08 10:48 , Vinay Sajip wrote:

Terry Reedy<tjreedy udel.edu> writes:

The behavior matches the doc: Popen.stdin If the stdin argument was PIPE, this attribute is a file object that provides input to the child process. Otherwise, it is None. Right, but it's not very helpful, nor especially intuitive. Why does it have to be None in the case where you pass in a file object? Is there some benefit to be gained by doing this? Does something bad happen if you store that file object in proc.stdin / proc.stdout / proc.stderr?

proc.stdin, proc.stdout, and proc.stderr aren't meant to be a reference to the file that got connected to the subprocess' stdin/stdout/stderr. They are meant to be a reference to the OTHER END of the pipe that got connected. When you pass in a normal file object there is no such thing as the OTHER END of that file. The value None reflects this fact, and should continue to do so.

-Phil

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