How does using type annotations in Python affect performance and program execution?

Type annotations in Python are used for static code analysis and improving readability, but do not affect performance at runtime. Python is a dynamically typed language, and annotations do not impose restrictions on types during program execution.

For example, annotations help tools like mypy check types before running, but the interpreter ignores them during execution:

def greet(name: str) -> str:
    return 'Hello, ' + name

Here, name: str is a hint, but Python will not verify that the argument is actually a string type, nor will it speed up the function. Thus, annotations are useful for development and maintenance of code, but do not influence the speed or behavior of the program during runtime.