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

Comece pelas implementações de get() e contains() de os._Environ descritas na issue e examine como as chaves ausentes são tratadas atualmente. A alteração estará concluída quando esses métodos evitarem gerar e capturar imediatamente KeyError, preservando ao mesmo tempo seus resultados existentes para chaves ausentes.