import os;
import sys;
filePathSrc="C:/folder/"
for root, dirs, files in os.walk(filePathSrc):
    for fn in files:
        if fn[-4:] == '.txt' or fn[-5:] == '.html':
            notepad.open(root + "\\" + fn)
            notepad.runMenuCommand("Encoding", "Convert to UTF-8")
            notepad.save()
            notepad.close()