Type hints are not enforced at runtime

Question

Accepted Answer

Python does not enforce type hints at runtime - they are annotations only. Passing the string 'ha' where an int is annotated raises no error because Python never checks the annotation. The expression 'ha' * 2 is perfectly valid Python (string repetition), so it prints 'haha'. This is the key fact about type hints: they exist for tools and humans, not for the interpreter. If you want runtime validation, you need a library like Pydantic or explicit isinstance checks.