TextBuffer.setText

Deletes current contents of buffer, and inserts text instead. This is automatically marked as an irreversible action in the undo stack. If you wish to mark this action as part of a larger undo operation, call [gtk.text_buffer.TextBuffer.delete_] and [gtk.text_buffer.TextBuffer.insert] directly instead.

If len is -1, text must be nul-terminated. text must be valid UTF-8.