That ignores how python scoping works. Built-ins are actually the last thing python checks.

You can override the built-ins by re-defining the symbol in any of: local functions, enclosing functions, or the global scope and it will impact the entirety of that scope.

You missed the point. It’s not about names themselves. What happens if I want to lookup bytestring-named attributes on a class defined in a Unicode-string module or vice versa?

Ahh, the wording screwed me up.

If I'm understanding your comment correctly this time, it would look something like:

getattr(thing, b'attribute_name')

I guess you could make it work as long as everything is ascii right? And if it's not then raise exception.

If it's not ascii, you would just do:

getattr(thing, u'attribute_with_unicode_characters')

This would work in both python 2.7 and 3.9 (probably works with other 3.X versions but it's the one I actually tried).

    str = int

is perfectly valid python. So having str mean different things in different modules is already possible.

You missed the point. It’s not about names themselves. What happens if I want to lookup bytestring-named attributes on a class defined in a Unicode-string module or vice versa?

I'm afraid I don't understand your question completely, so I'll answer what I guess you mean. Let's say you have a function in one module that expects a bytestring. This function is called from another module, and a unicode string is passed. What happens?

Well python is a duck-typed language, so it will handle the unicode string as if it was a bytestring, and this may or may not work correctly. It's up to the modern code to interface correctly with the legacy code. This could mean manually converting between bytestring and unicode string.