Function Annotations

In Python function annotations helps us to attach metadata to function parameters and return values, add

IDEs and libraries could use annotations to indicate the function’s expected input and return types.

function annotations syntax

We use the following syntax to annotate function parameters and return value. By adding a color (:) after a parameter and an arrow (->) for return types

  def function_name(parameter: annotation) -> return_annotation:
      pass

Annotating functions parameters

  def add(a: int, b: int):
      return a + b

In this example:

The parameters a and b are annotated with int, giving us hints that they should be integers

Annotating functions return value

  def add(a: int, b: int) -> int:
      return a + b

In this example:

The parameters a and b are annotated with int, giving us hints that they should be integers
The return type is annotated with int

Function annotations with default arguments

  def add(a: int = 10, b: int = 20) -> int:
      return a + b