To do this in Python (i.e. not wrapping scp through subprocess.Popen or similar) with the Paramiko library, you would do something like this:
import os
import paramiko
ssh = paramiko.SSHClient()
ssh.load_host_keys(os.path.expanduser(os.path.join("~", ".ssh", "known_hosts")))
ssh.connect(server, username=username, password=password)
sftp = ssh.open_sftp()
sftp.put(localpath, remotepath)
sftp.close()
ssh.close()
(You would probably want to deal with unknown hosts, errors, creating any directories necessary, and so on).