Data classes

@dataclass writes the repetitive parts of a class for you: __init__, a readable __repr__ and __eq__, all generated from the field annotations. Give a field a default with =, and use field(default_factory=list) when each object needs its own fresh list.

How it reads

• Each name: type line becomes a constructor parameter
• The generated __repr__ prints every field
• The generated __eq__ compares field by field

Cloud tip: Add frozen=True (@dataclass(frozen=True)) for objects that should never change after they are made.