sentinel¶

basedpython adds a sentinel statement for declaring named sentinel objects:

sentinel MISSING

transpiles to:

from typing_extensions import Sentinel

MISSING = Sentinel("MISSING")

syntax¶

sentinel NAME declares a module-level sentinel. the form is a soft keyword followed by a single identifier and a newline. the identifier becomes the sentinel name (used both as the python variable and as the string passed to sentinel(...))

sentinel MISSING
sentinel UNSET

scope¶

sentinel is a soft keyword: in any other position (sentinel = 5, sentinel(...)) it parses as a regular identifier

polyfill¶

PEP 661 proposes a builtin sentinel function. until python ships it, typing_extensions.Sentinel is used