os._Environ.get() and __contains__() raise and catch KeyError internally

Feature or enhancement

Proposal:

Since os._Environ is a subclass of collections.abc.Mapping, its get() and __contains__() methods are implemented in terms of __getitem__(). By forwarding to __getitem__(), a KeyError is raised when the key does not exist. This KeyError is then immediately caught and swallowed.

Handling this exception is extra, avoidable work. _Environ can check its internal dictionary directly which is more efficient.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-156492

Comience con las implementaciones de get() y contains() de os._Environ descritas en el issue y examine cómo se gestionan actualmente las claves que faltan. El cambio estará completo cuando esos métodos eviten provocar y capturar inmediatamente KeyError, conservando al mismo tiempo sus resultados actuales para las claves que faltan.