with open ("utf8.txt", encoding="utf8") as inp, open("cp1251.txt", "w", encoding="cp1251") as out:
    out.write(inp.read())

......
    def load(self, data, data_encoding=None):
        if data_encoding is None:
            data_encoding = self.defaultencoding
        self.Lock.acquire()
        for line in data:
            self.Container.append(line.translate(None, "\r\n").decode(data_encoding, "replace"))
        if self.StringVar is not None:
            try:
                self.StringVar.set(len(self.Container))
            except RuntimeError:
                pass
        self.Lock.release()
......
    def dump(self, outfile, data_encoding=None, remove=False):
        if data_encoding is None:
            data_encoding = self.defaultencoding
        self.Lock.acquire()
        with open(outfile, "a") as out:
            for item in self.Container:
                out.write("{0}\n".format(item.encode(data_encoding, "replace")))
        if remove:
            self.Container = []
        if self.StringVar is not None:
            try:
                self.StringVar.set(len(self.Container))
            except RuntimeError:
                pass
        self.Lock.release()
......

......
    #Сюда нужно отправлять что типа такого 
#with open("bla.txt", encoding=encoding) as inpt:
#some.load(inpt)
    #Атрибут загрузки из последовательности(или итератора)
    def load(self, data):
        self.__Lock.acquire()
        for line in data:
            self.__Container.append(line.strip("\r\n"))
        self.__Lock.release()
......
    #Атрибут дампа всех элементов контейнера в файл
    def dump(self, outfile, encoding):
        self.__Lock.acquire()
        with open(outfile, "a", encoding=encoding) as out:
            for item in self.__Container:
                out.write("{0}\n".format(item))
        self.__Lock.release()
......

#with open("bla.txt", encoding="utf8") as inpt:
#some.load(inpt)