Surely readline() "rtype" is string not int as stated (and not bytes as some might expect).
Also it is not totally unambiguous what happens on a timeout so it would help to clarify in docs that on a timeout
it does NOT return with what it has read so far, rather it leaves all that in the buffer ready for a future read and returns nothing.
Likewise clarify that if timeout=0 but there is no newline it DOES return what it has read so far (NOT None).
At least this is what I think it does and/or is supposed to do!
Python docs are generally not too explicit about what is the proper treatment, so perhaps all the more reason to
clarify the interpretation adopted?