import paramiko

sftpURL   =  'sftp.somewebsite.com'
sftpUser  =  'user_name'
sftpPass  =  'password'

ssh = paramiko.SSHClient()
# automatically add keys without requiring human intervention
ssh.set_missing_host_key_policy( paramiko.AutoAddPolicy() )

ssh.connect(sftpURL, username=sftpUser, password=sftpPass)

ftp = ssh.open_sftp()
files = ftp.listdir()
print files

['.bash_logout', '.bash_profile', '.bashrc', '.mozilla', 'testfile_248.xml']

>>> for i in ftp.listdir():
...     lstatout=str(ftp.lstat(i)).split()[0]
...     if 'd' in lstatout: print i, 'is a directory'
...

>>> for i in ftp.listdir():
...     lstatout=str(ftp.lstat(i)).split()[0]
...     if 'd' not in lstatout: print i, 'is a file'
...