python binary struct class

struct.py

import struct


class Struct:
    _fields = None  # type: tuple
    _size = None  # type: int

    @classmethod
    def size(cls):
        if cls._size is None:
            cls._size = sum(field_cls.size() for field_cls, _ in cls._fields)
        return cls._size

    @classmethod
    def unpack(cls, _bytes: bytes):
        if cls._fields is None:
            raise Exception("_serialize field required")
        instance = cls()
        read_pos = 0
        for field_cls, field_name in cls._fields:
            if issubclass(field_cls, StructField) or issubclass(field_cls, Struct):
                setattr(instance, field_name, field_cls.unpack(_bytes[read_pos:read_pos + field_cls.size()]))
                read_pos += field_cls.size()
            else:
                raise TypeError("All Struct fields must be subclass of Struct or StructField")
        return instance


class StructField:
    _format = None  # type: str
    _primitive_struct = None  # type: struct.Struct

    @classmethod
    def size(cls) -> int:
        if cls._primitive_struct is None:
            cls._primitive_struct = struct.Struct(cls._format)
        return cls._primitive_struct.size

    @classmethod
    def unpack(cls, _bytes: bytes):
        if cls._primitive_struct is None:
            cls._primitive_struct = struct.Struct(cls._format)
        return cls._primitive_struct.unpack(_bytes)[0]


class UInt32(StructField):
    _format = "<I"

class UInt16(StructField):
    _format = "<H"


class IPEndPoint(Struct):
    _fields = (
        (UInt32, "ip_address"),
        (UInt16, "port")
    )

binary = b"\xFA\xBB\x1C\x09\xFF\xFF"
ep = IPEndPoint.unpack(binary)
print(ep.ip_address, ep.port)