def update_ok_button(self):
        """Updates self.ok_button. No other side-effects."""
        send_amount = self.send_amount_e.get_amount()
        recv_amount = self.recv_amount_e.get_amount()
        self.ok_button.setEnabled(bool(send_amount) and bool(recv_amount))
Updates self.ok_button. No other side-effects.
electrum/gui/qt/swap_dialog.py