Difficulty while using Python Paramiko to execute command on remote server

Was trying to SSH from one linux server to another using Paramiko library but getting the

    import sys
    import paramiko

    hostname ="****"
    password="no password provided"
    source=""
    username="***"
    port=22

    key_file_path="/root/.ssh/id_rsa"

    #printing key
    file=open(key_file_path,"r")
    print file.read()



    try:
            ssh=paramiko.SSHClient()
            ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())





 ssh.connect(hostname,port,username,password,key_filename=key_file_path,passphrase=None)
            #ssh_session=ssh.get_transport().open_session()
            stdin,stdout,stderr = ssh.exec_command('uptime')
            output=stdout.readlines()
            error=stderr.readlines()

            print("STDOUT output")
            print(output)
            print("output object type")
            type(output)
            print("STDERR output")
            print(error)

    except Exception, e:
            print e
            print "exception occoured"

Output :-

STDOUT output :- []
output object type :- 
STDERR output [u'Connecting to **.**.**.***:****\r\n']

As I am new so i have searched all over the net and have build till this point but I'm stuck at this point and not finding as to why is the error please can anyone help me.....

And also have viewed all related questions but couldn't find as to why the error is occouring...