Problem with authentification

[Mykle]

Hi, I'm french so I apologize for mistakes I'm about to make in
english...

I installed Paramiko on a Debian Server for making connections with an
SSH
Server and here's my issue:

I create a transport connection with the server for getting files from
it.
The server asks an authentification but the public key is kept by the
SSH
Server and recognize the computer by his public key username at
computername,
the server have a username for the public key. There's no password
anyway !
Until now, I use a bash script which make an ssh connection with the
Server
(like 'ssh -x -a username at sshadress'), but I want to change that
for some
verification reasons. I mustn't have to put any key in the code...
What I
want is to connect to the Server and that this one accept this
connection by
only the recognization of the username at computername. The
documentation
doesn't really help me and I'm not pretty much good in Python (maybe
that
explains why I'm writing this mail...*sic*).

Here's the begining of my code:

import paramiko
TR = paramiko.Transport((sshAdress,22))
....

.... Yeah I know, it's like there was nothing...

Thank you for your help.

Michael.