def _spawn(self, ddconfig):
        """
        Spawn a process by defined command.
        Method is only called if no window is associated. This is either on the
        first call to show or if the window was killed.
        The process id of spawned process is saved and compared to new windows.
        In case of a match the window gets associated to this DropDown object.
        """
        name = ddconfig.name
        if name not in self._spawned:
            if not self._spawned:
                hook.subscribe.client_new(self.on_client_new)
            pid = self.qtile.spawn(ddconfig.command)
            self._spawned[name] = ddconfig.match or Match(net_wm_pid=pid)

        Spawn a process by defined command.
        Method is only called if no window is associated. This is either on the
        first call to show or if the window was killed.
        The process id of spawned process is saved and compared to new windows.
        In case of a match the window gets associated to this DropDown object.
        
libqtile/scratchpad.py