Private underscore prefix (ARCH2009)

Key python.naming.private-underscore-prefix · Severity info · Category naming

Private members meant for internal use should be marked with a single leading underscore per Python convention. Without that signal, outside code may rely on them and create brittle coupling.

Incorrect

class Cache:
    def __init__(self):
        self.store = {}  # internal but unprefixed

    def evict(self):  # internal helper, unprefixed
        self.store.clear()

Correct

class Cache:
    def __init__(self):
        self._store = {}

    def _evict(self):
        self._store.clear()

Fix

Add a single leading underscore to internal members and methods (e.g. store → _store).