In https://docs.python.org/3/library/io.html it is forgotten to say whether '\n' is appened to the return value of readline().

It is also unclear what happens if the last line not terminated by '\n' is read.

It is also unclear what is returned if a text file (say with '\r\n' terminators) is read. Is it appended to the return value '\n', '\r\n' or nothing?

I agree that the documentation should be clearer about the first two points. Considering that the "input" function and by default the "str.splitlines" method both behave differently, I often had to re-learn this when I had less Python experience.

The expected behaviour as I understand is the line terminator is included if it was read. It is not included if the size limit or EOF was reached first. The Python 2 documentation <https://docs.python.org/2/library/stdtypes.html#file.readline> is clear about both the newline being included and EOF behaviour.

Regarding text files, if you mean the "TextIOWrapper.readline" method, I think it is reasonable to assume you get the translated line endings as specified by the constructor's "newline" argument: <https://docs.python.org/3/library/io.html#io.TextIOWrapper>. Newline='' and newline='\r\n' would keep the '\r\n' terminators, and newline=None would translate them to '\n'.