python operation ssh realize server log download method

#coding:utf-8
"""
  Example of ssh operation Implemented server log download
  2012-08-24
  yywolf
"""
import paramiko
import time
hostname="????"
port=22
username="app"
password="????"
if __name__=="__main__":
#  .log_to_file('')
  s = ()
  s.load_system_host_keys()
  s.set_missing_host_key_policy(()) 
  (hostname,port,username,password,timeout=4)
  stdin,stdout,stderr = s.exec_command("sh ~/log/check")
  print ()
  ()
  #sftp
  t = ((hostname,port))
  (username=username,password=password)
  sftp = .from_transport(t)
  files = ("/home/app/log/")
  for f in files:
    print f
  filetime = ('%Y-%m-%d',(()))
  #The file to be downloaded and the name of the downloaded file.
  ("/home/app/log/","C:\\Users\\Administrator\\Desktop\\")   
  ("/home/app/log/"+filetime+".","C:\Users\Administrator\Desktop\\"+filetime+".")
  #RASkey
  pkey_file = "E:\\yy\\tools\\key\\"
  key = .from_private_key_file(pkey_file)
  s = ()
  s.load_system_host_keys()
  s.set_missing_host_key_policy(()) 
  (hostname,port,username,pkey=key)
  stdin, stdout, stderr = s.exec_command("ls -l /home/app/log")
  print ()
  ()
  raw_input()