There is no contradiction between “constructors cannot fail” and “fail early”, nobody is arguing the constructor should do fallible things and then hide the failure.

What you should do is the fallible operation outside the constructor, before you call __init__, then ask for the opened file, socket, lock, what-have-you as an argument to the constructor.

Fallible initialisation operations belong in factory functions.

The real problem is that constructors and factory functions are distinct in the first place. They aren't, in Rust, and it's much easier to reason about and requires far less verbiage to write.

Why though?