Function annotation is one of the most unique features of Python 3. The official documentation states the following:
"Function annotations are completely optional metadata information about the types used by user-defined functions."
However, they are not restricted to type hinting; also, there is no single feature in Python and its standard library that leverages such annotations. This is why this feature is unique – it does not have any syntactic meaning. Annotations can simply be defined for a function and can be retrieved in runtime, but that is all. What to do with them is left to the developers.
Let's take a look at their general syntax and possible uses in the following sections
