help coding for decode filtering

[volcano63]

If your function accepts input line by line, you may use function-level caching. I will show you how to use mutable default value to this end

Let's start by splitting the line unconditionally

def parse_mochad_line(self, line, _house_unit=[]):
    elements = line.split()
    classifier = ''.join(elements[2:4])
    if classifier == 'RxRFSEC':
        ......
    elif classifier == 'RxRF':
        .....
    elif classifier == 'RxPL':
        if not house_unit:
            _house_unit.append(...)
         else:
            ......
            _house_unit.clear()

Pay attention - you cannot assign _house_unit, because that will ruin caching mechanism