... one of #TIMTOWTDI #workaround​s for the #Python #thorn_in_backside #wart
via (shallow) copy of the module-global🙃 (mutable) structure it is ...

from dataclasses import dataclass, field

default = [ 2 ]

@dataclass
class Initial_Mutable_Default:
# Look Ma, no "__post_init__()"!
attr :list[ int ] = field( default_factory = lambda: list( default ) )

print( Initial_Mutable_Default() )
🤷🏽‍♂️