The online Python 3 documentation for bytes.rpartition and bytearray.rpartition (https://docs.python.org/3/library/stdtypes.html#bytes.rpartition) incorrectly states:

"If the separator is not found, return a 3-tuple containing a copy of the original sequence, followed by two empty bytes or bytearray objects."

This seems to have been copied without modification from bytes.partition where the statement is correct. The statement for rpartition should be:

"If the separator is not found, return a 3-tuple containing two empty bytes or bytearray objects, followed by a copy of the original sequence."

Thanks for the report. Would you like to create a PR for this?

The test for this behavior is at https://github.com/python/cpython/blob/3d07c1ee1d2d475b74816117981d6ec752c26c23/Lib/test/test_bytes.py#L655
Doc file to be changed : https://github.com/python/cpython/blob/master/Doc/library/stdtypes.rst

OK, I can give it a try. I need to read up on the procedures for doing so, first, though, so it may take a while.

You can find more information about the process at https://devguide.python.org/

New changeset efc48701496ef020e896fc6a91af3c0c612ac69a by Inada Naoki (pewscorner) in branch 'master':
bpo-36416: Correct bytes.rpartition documentation (GH-12543)
https://github.com/python/cpython/commit/efc48701496ef020e896fc6a91af3c0c612ac69a

New changeset 04b114eede82c7ffd7b3d9b40e8bf707780b022b by Miss Islington (bot) in branch '3.7':
bpo-36416: Correct bytes.rpartition documentation (GH-12543)
https://github.com/python/cpython/commit/04b114eede82c7ffd7b3d9b40e8bf707780b022b

messages: + msg338735
versions: + Python 3.8