Create a distinct nominal type for type hints, enabling stronger type checking while preserving runtime representation.

Introduce a new nominal type for type annotations to improve type safety and code clarity.

When you need a distinct type alias that is treated as a separate type by type checkers (e.g., UserId = NewType('UserId', int)) to prevent mixing of similar raw types.

Typically placed at the top of a module in the imports section, or within type stub files; used when defining domain‑specific types like IDs, identifiers, or specialized numeric types.

from typing import NewType

from typing import NewType

<name>, <base_type>

• int
• str
• float
• Any
• List
• Dict

• typing.NewType

Using NewType as a runtime type; confusing with typing.NewAlias; forgetting to call NewType as a callable.

typing.NewAlias, typing.TypeAlias, typing.Alias

Confusing NewType with a simple alias (type Alias = int) which does not create a distinct type for type checkers.

• typing imports
• type hints
• NewType
• TypeAlias

NewType creates a distinct nominal type only for static type checkers; at runtime it returns a function that returns its argument with a custom __name__.

Signals to type checkers and readers that the value is a specialized kind of the base type, preventing accidental mixing of similar IDs.

Think of creating a distinct ID type to avoid mixing user IDs with order IDs.