Problems with scp script in Python

[jhlobin at gmail.com]

I have an SCP script that auto completes just fine from the terminal window in Pi.  When I use either subprocess or os to try and have it run under Python it does not do the file transfer from Pi to my Ubuntu machine.  What am I doing wrong?  Here is the script: 

from subprocess import call 
cmd='scp -i id_rsa sample.txt jack at 192.168.1.103 /home/jack/pi_data' 
call (cmd.split ()) 

Thank you