Download files over SSH using Python

You need to explicitly specify the remote path:

import os
import paramiko 
ssh = paramiko.SSHClient()
ssh.connect('10.170.21.93', username="abhishek", password="@bhishek$")
sftp = ssh.open_sftp()
localpath = 'abc.txt'
remotepath = '/opt/crestelsetup/patchzip/abc.txt'
sftp.put(localpath, remotepath)
sftp.close()
ssh.close()

As per Martin Prikryl's comment, the following code line is highly discouraged as it opens you up against man in the middle attack, however, it can be a temporary fix for missing host keys

ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())