[plum.structure] Tutorial: Packing Structures

This tutorial shows the variations of how to pack structure member values into a bytes buffer.

The first way to pack a structure requires instantiating the structure type and calling the pack() method:

>>> from plum.structure import Member, Structure
>>> from plum.int.little import UInt8, UInt16
>>>
>>> class MyStruct(Structure):
...     m1: int = Member(cls=UInt8)
...     m2: int = Member(cls=UInt16, default=2)
...
>>> MyStruct(m1=1, m2=2).pack()
bytearray(b'\x01\x02\x00')

Alternatively, pass the structure type as the first argument and the value of the structure (in list, tuple, or dict form) as the second argument. Members with a default value defined in the structure type may be left unspecified:

>>> from plum import pack
>>>
>>> # dict mapping
>>> pack(MyStruct, {'m1': 1})  # unspecified members default
bytearray(b'\x01\x02\x00')
>>>
>>> # list
>>> pack(MyStruct, [1, 0])
bytearray(b'\x01\x00\x00')
>>>
>>> # tuple
>>> pack(MyStruct, (1, 0))
bytearray(b'\x01\x00\x00')

Tip

These alternatives may yield slightly faster performance since it avoids instantiating the structure type.