Flask stream generated .zip file

zipstream.py

import zipfile

class StreamedBytesIO(object):
    def __init__(self):
        self._b = bytearray()
        self._pos = 0

    def seek(self, *args):
        raise AttributeError('sorry')

    def tell(self):
        raise AttributeError('sorry')

    def flush(self, *args):
        pass

    def close(self, *args):
        pass

    def write(self, data):
        if self._pos + len(data) > len(self._b):
            self._b.extend(0 for _ in range(max(len(data), len(self._b))))
        self._b[self._pos:self._pos + len(data)] = data
        self._pos += len(data)
        return len(data)

    def get_chunk_and_reset(self):
        result = memoryview(self._b)[:self._pos].tobytes()
        self._pos = 0
        return result

def generate():
    yield b'' # flushing response status and headers to client
    
    b = StreamedBytesIO()
    archive = zipfile.ZipFile(b, mode='w', compression=zipfile.ZIP_DEFLATED)
    for path_in_archive, data in get_a_lot_of_files():
        archive.writestr(path_in_archive, data)

        yield b.get_chunk_and_reset()

    archive.close()
    yield b.get_chunk_and_reset()

@app.route('/large.zip')
def generate_large_zip():
    return Response(generate(), mimetype='application/zip')