example.py

note = Types.Note()

note.title = "I will soon have application data"
note.content = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>"
note.content += "<!DOCTYPE en-note SYSTEM \"http://xml.evernote.com/pub/enml2.dtd\">"
note.content += "<en-note>Content goes here</en-note>"
note = note_store.createNote(note)

# Now we have the note GUID and can add applicationData

dkey = "my-consumer-key" # the first part of your API key
dval = "I'm the value: an arbitrary string"

note_store.setNoteApplicationDataEntry(note.guid, dkey, dval)
note = note_store.updateNote(note)