Is subprocess.Popen completely broken?

Jeffrey Froman jeffrey at
Thu Mar 27 16:04:43 CET 2008

Skip Montanaro wrote:

> I am trying to replace os.system calls with subprocess.Popen.  This simple
> example fails miserably:
>>>> proc = subprocess.Popen ("ls /tmp")

Popen expects a list of program arguments. When passed a single string
instead of a list, as in your example, it assumes that the string is the
command, and looks for an executable named "ls /tmp", which of course does
not exist.

Split your command into a list of separate parameters, with the executable
as the first parameter, and it will work:

>>> subprocess.Popen(['ls',  '/tmp'])
<subprocess.Popen object at 0xb7c569ec>
>>> (ls output here)


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