I want to send a zip file through SOAP (from a SOAP client to a SOAP server) in python.
Following the reading of this SO question, I choose to use suds as my python
Attachments are best way to send binary file through SOAP. If you can't use any other method but only SOAP, just encode your binaries with Base64 and paste it into SOAP method as a parameter. It isn't pure, but works great with small attachments. Large binaries? Use FTP, WebDAV and all others native ways for sending files between hosts.