popen4 not returning output

[hortitude]

I am trying to run the following script:
#!/usr/bin/python

import popen2

commandToRun = """scp scp_trial.py user@host:/targetDirectory"""
#commandToRun = "ls"
print commandToRun
p_out, p_in = popen2.popen4 (commandToRun)

theOut = p_out.readlines ()
print theOut
When I run this command with the "ls" command I see the output.
When I run this with the scp command I do not see the output of my
command -- however the file is successfully transfered. How can I see
the output?

Thanks