Python class to record a GUID as done processed

DoneList.py

class DoneList:
    FILE_NAME = 'done_list.txt'

    def __init__(self):
        self.done_set = set()
        # Load file ...
        try:
            with open(DoneList.FILE_NAME, "r") as fp:
                for line in fp:
                    annotation_id = line.strip()
                    self.done_set.add(annotation_id)
        except FileNotFoundError:
            print("%s not found" % DoneList.FILE_NAME)

    def add(self, annotation_id):
        self.done_set.add(annotation_id)

        # append file
        with open(DoneList.FILE_NAME, "a") as fp:
            fp.write("%s\n" % annotation_id)

    def __contains__(self, key):
        return key in self.done_set