What does the -> (dash-greater-than arrow symbol) mean in a Python method signature? [duplicate]

Answer 1

This is function annotations. It can be use to attach additional information to the arguments or a return values of functions. It is a useful way to say how a function must be use. Functions annotations are stored in a function's __annotations__ attribute.

Use Cases (From documentation)

• Providing typing information

  • Type checking
  • Let IDEs show what types a function expects and returns
  • Function overloading / generic functions
  • Foreign-language bridges
  • Adaptation
  • Predicate logic functions
  • Database query mapping
  • RPC parameter marshaling

• Other information

  • Documentation for parameters and return values

From python-3.5 it can be used for Type Hints