Recursively searches for files with the specified extension in the source folder and moves them into the destination folder. You can replace "fileExtension == extension" with "fileExtension != extension" to move every file except for the specified extension.

file_mover.py

import sys, os

source = "./Source_Folder/"
destination = "./Destination_Folder/"
extension = ".xml"
fileList = []

for root, folders, files in os.walk(source):
  for f in files:
		fileName, fileExtension = os.path.splitext(os.path.join(root,f))
		if (fileExtension == extension):
			fileList.append(os.path.join(root,f))

for f in fileList:
	os.rename(f,destination + f.split('/')[-1])