What does the bracket [ ] mean when it comes after a class name?

Question

For example,

class BasicTransitionFunction(TransitionFunction[GrammarBasedState]):
      ...

where TransitionFunction is the base class of BasicTransitionFunction, and GrammarBasedState is also a class name. I only know that [] can be used to indexed arrays. What does it mean here?

Answer 1

这是泛型类型的语法。就像@Sraw所说，这意味着这TransitionFunction是一个泛型类型。例如，List是泛型类型，因此您可以拥有List[Int].

这与 C++ 模板的想法相同（例如std::vector<int>）。

所以这是 a Between sBasicTransitionFunction的子类。TransitionFunctionGrammarBasedState