Easiest way to copy all fields from one dataclass instance to another?

Question

Let\'s assume you have defined a Python dataclass:

@dataclass
class Marker:
    a: float
    b: float = 1.0
         


        

Answer 1

@dataclass
class Marker:
    a: float
    b: float = 1.0

marker_a = Marker(0.5)

marker_b = Marker(**m1.__dict__)

marker_b

# Marker(a=0.5, b=1.0)

If you didn't want to create a new instance, try this:

marker_a = Marker(1.0, 2.0)
marker_b = Marker(11.0, 12.0)

marker_b.__dict__ = marker_a.__dict__.copy()

# result: Marker(a=1.0, b=2.0)

Not sure whether that's considered a bad hack though...