download/upload files to remote windows server using python

When in windows do as the windows-users do.

If you can't install additional software on the server, you need to mount the drive, and interact with the remote files like they are local files.

You mention that you have too many remote servers to connect to. Why not pick one drive letter, and reuse it for each server you need to connect to?

With net use you can mount from the command line.

Syntax for net use

net use p: /delete:yes
net use p: \\remote_host\share_name password /user:domain\user

Use Python's subprocess package to run the mount commands. Subprocess tutor.

import subprocess

# Make sure the drive isn't mounted.
try:
    subprocess.call('net use p: /delete:yes', shell=True)
except:
    # This might fail if the drive wasn't in use.
    # As long as the next net use works, we're good.
    pass

for host in ("host1", "host2"):
    # mount(map) the remote share.
    subprocess.call('net use p: \\%s\share_name password /user:domain\user' % host, shell=True)
    with open("p:\path\remote-file.txt", "r") as remote_file:
        # do stuff
    # dismount(map) the drive
    subprocess.call('net use p: /delete:yes', shell=True)

(Don't have a windows box and network to test this on.)

Use the win_unc library: http://covenanteyes.github.io/py_win_unc/

This will allow you to do normal modifications to file paths as well as log in as a different user.