Bytes stream in Python

    @staticmethod
    def from_bin(dataB):
        reader=io.BytesIO(dataB)
        length1= reader.read(4)
        length2=reader.read(4)
        length3=reader.read(4)
        macs=reader.read(length1)
        uid=reader.read(length2)
        signature=reader.read(length3)
        reader.close()

        message=Message(macs,uid,signature)
        return message

References :
https://docs.python.org/3/library/io.html#io.BytesIO http://chimera.labs.oreilly.com/books/1230000000393/ch05.html#_solution_78
https://docs.python.org/2/library/io.html