Reader

class Reader:
    def __init__(self, filename):
        self._delim_ = re.compile(r'\n', re.DOTALL)
        self._size_ = -1
        self._stack_ = []
        self._current_ = type('Reader.Current', (), dict(state=None))
        self.Push(filename)
    def Push(self, filename):
        self._stack_.append(type('Reader.State', (), dict(filename=filename, buffer='', element=0)))
        self._current_.state = self._stack_[-1]
        self._current_.state.file = open(self._current_.state.filename)
    def Pop(self):
        state = self._stack_.pop()
        if len(self._stack_) > 0:
            self._current_.state = self._stack_[-1]
        state.file.close()
        return state
    def __iter__(self):
        current = self._current_
        while True:
            if not current.state:
                break
            buffer = current.state.file.read(self._size_)
            if len(buffer) == 0:
                buffer = current.state.buffer
                self.Pop()
                if buffer != '':
                    yield buffer
                    if current.state:
                        continue
                break
            current.state.buffer += buffer
            while True:
                match = self._delim_.search(current.state.buffer)
                if not match: break
                current.state.element += 1
                buffer = current.state.buffer
                current.state.buffer = current.state.buffer[match.end():]
                yield buffer[0:match.end()], current.state.element