How about just presenting pseudo code with the caveat that that's for the base str and bytes classes only, and then stipulating that for subclasses the return value is still a str/bytes/bytearray instance, and leaving it at that? After all the point of the Python code is to show what the C code should do in a way that's easy to grasp -- giving a Python implementation is not meant to constrain the C implementation to have *exactly* the same behavior in all corner cases (since that would lead to seriously contorted C code).

On Fri, Mar 27, 2020 at 1:02 PM Dennis Sweeney <sweeney.dennis650@gmail.com> wrote:

I was trying to start with the the intended behavior of the str class, then move on to generalizing to other classes, because I think completing a single example and *then* generalizing is an instructional style that's easier to digest, whereas intermixing all of the examples at once can get confused (can I call str.removeprefix(object(), 17)?). Is something missing that's not already there in the following sentence in the PEP?

Although the methods on the immutable ``str`` and ``bytes`` types may make the aforementioned optimization of returning the original object, ``bytearray.removeprefix()`` and ``bytearray.removesuffix()`` should always return a copy, never the original object.

Best,
Dennis
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