PaperSize()

Special typing form to define literal types (a.k.a. value types).

Usage

Source

PaperSize(
    self,
    *parameters,
)

This form can be used to indicate to type checkers that the corresponding variable or function parameter has a value equivalent to the provided literal (or one of several literals):

def validate_simple(data: Any) -> Literal[True]:  # always returns True
    ...

MODE = Literal['r', 'rb', 'w', 'wb']
def open_helper(file: str, mode: MODE) -> str:
    ...

open_helper('/some/path', 'r')  # Passes type check
open_helper('/other/path', 'typo')  # Error in type checker

Literal[…] cannot be subclassed. At runtime, an arbitrary value is allowed as type argument to Literal[…], but type checkers may impose restrictions.