Class and Instance Variable Annotations

Type annotations can also be used to annotate class and instance variables in class bodies and methods.

In particular, the value-less notation: a: int allows one to annotate instance variables that should be initialized in __init__ or __new__. See the syntax in the picture.

As one knows, defining class member variables is not mandatory but it’s useful for providing autocomplete functionality while coding.

The differences between class and instance variables are discussed in the following idea