How to use ssh-agent in windows in python?

[Fc Zwtyds]

Hi,
   I am using cygwin on Windows 8.1. These two commands work fine in cygwin:
ssh-agent -s
ssh-add ~/.ssh /id_rsa
   I tried to use them on windows cmd and it worked fine. Now I am going 
to use python to write code to implement the above command.
os.system('ssh-agent -s')
os.system('ssh-add id_rsa')
There was an error:
Could not open a connection to your authentication agent.

Thank you and your time.