Question 1

Are type hints enforced at runtime in Python?

Accepted Answer

No; annotations are metadata read by static analysis tools such as mypy and Pyright, and they do not stop Python from passing a value of a different type at runtime.

Question 2

How do you express a value that may be one of two types or None?

Accepted Answer

Use the union syntax X | Y and X | None (since Python 3.10), or Union and Optional from typing in older versions; Optional[X] means X | None and not "an optional parameter".

Question 3

What is a Protocol in typing?

Accepted Answer

A Protocol describes the required behavior (methods and attributes) and accepts any class that matches it structurally without explicit inheritance; it is a static form of duck typing.

Question 4

What is the role of TypeVar and Generic in Python?

Accepted Answer

A TypeVar represents an unknown type that must stay the same across parts of a signature, and Generic lets you define a class that preserves the type of what it holds; since Python 3.12 there is also the shorthand syntax def first[T](...) and class Box[T].

Question 5

When should you use TypedDict with JSON data?

Accepted Answer

TypedDict describes the keys of a dict and the types of its values for static checkers, while the value remains a plain dict at runtime with no validation or conversion.

Question 6

What are Final and Literal used for?

Accepted Answer

Final marks a name that should not be reassigned (according to type checkers), and Literal restricts a value to a fixed set of literal values such as "asc" or "desc".

Question 7

When do you use @overload?

Accepted Answer

When a single function returns different types depending on the types or values of its arguments; you write several signatures decorated with overload for the type checker, followed by one real implementation with a general signature.

Question 8

What is the difference between Any and object in type hints?

Accepted Answer

Any disables checking: it accepts any value and allows any operation on it. object also accepts any value but does not allow special operations on it until the type is narrowed.

Question 9

What are TypeGuard and TypeIs for in type narrowing?

Accepted Answer

They declare that a boolean predicate function, when it returns True, has narrowed the type of its argument; TypeIs (since Python 3.13) narrows the type in both the True and False branches, while TypeGuard narrows only the True branch.

Question 10

How do you use typing to improve module boundaries without overdoing it?

Accepted Answer

Concentrate precise types on public interfaces and system boundaries (public module functions, domain types, protocols), and leave local variables to automatic inference.