Python is a dynamically-typed programming language, which means that the type of a variable is determined at runtime. However, with the release of Python 3.5, a new feature was introduced called variable annotations.
Variable annotations provide a way to annotate the type of a variable in the source code. This means that the type of the variable can be checked at compile-time instead of runtime, which can help catch errors earlier in the development process.
To annotate a variable in Python, you simply add a colon followed by the type after the variable name. For example:
age: int = 27
name: str = "John"
In the above example, we are declaring two variables, age and name, and annotating their types. The age variable is of type int, and the name variable is of type str.
Variable annotations are optional, so you can still declare variables without annotating their types. However, it is recommended to use variable annotations whenever possible, as they can help make your code more readable and easier to maintain.
In addition to simple types such as int and str, you can also annotate variables with more complex types such as lists and dictionaries. For example:
numbers: List[int] = [1, 2, 3]
person: Dict[str, Any] = {'name': 'John', 'age': 27}
In the above example, we are declaring two variables, numbers and person, and annotating their types. The numbers variable is of type List[int], which means it is a list of integers. The person variable is of type Dict[str, Any], which means it is a dictionary with string keys and values of any type.
In conclusion, variable annotations are a powerful feature in Python that can help catch errors earlier in the development process and make your code more readable and maintainable. They are easy to use and can be applied to simple and complex types alike.