Collection protocols (Reference)

This page documents stdlib traits that model Python-like collection behavior.

Contains (membership)

• Syntax: item in collection / item not in collection
• Hook: __contains__(self, item: T) -> bool
• Trait: Contains[T]

Len (length)

• Syntax: len(x)
• Hook: __len__(self) -> int
• Trait: Len

Iterable / Iterator (iteration)

• Syntax: for x in y:
• Hooks:
  • __iter__(self) -> Iterator[T]
  • __next__(self) -> Option[T]
• Traits:
  • Iterable[T]
  • Iterator[T]

Bool (truthiness)

• Syntax: if x: / while x:
• Hook: __bool__(self) -> bool
• Trait: Bool