The Annotated object

Type Hints

Python’s type hinting syntax can be used to annotate variables, function arguments, and return types with physical units. The following examples demonstrate the usage of type hints for annotating units:

# not compulsory
meters = Annotated[float, "meters"]
seconds = Annotated[float, "seconds"]

def speed(distance: "meters", time: "seconds") -> "meters / seconds":
    return distance / time

• Annotating a variable:

  from typing_extensions import Annotated
  
  distance: Annotated[float, "meters"]
  

• Annotating function arguments:

  from typing_extensions import Annotated
  
  def speed(distance: Annotated[float, "meters"],
                  time: Annotated[float, "seconds"]) ->
                  Annotated[float, "meters per second"]:
      return distance / time
  

• Annotating function return type:

  from typing_extensions import Annotated
  
  def speed(distance: Annotated[float, "meters"],
                 time: Annotated[float, "seconds"]) ->
                 Annotated[float, "meters per second"]:
      return distance / time
  

Note

Impunity is not yet compatible with all the different syntaxes introduced in the PEP 484.