New submission from Martin Panter:
I noticed that the newline translation in the io.StringIO class does not behave
as I would expect:
>>> text = "NL\n" "CRLF\r\n" "CR\r" "EOF"
>>> s = StringIO(text, newline="\r\n")
>>> s.getvalue()
'NL\r\nCRLF\r\r\nCR\rEOF' # Why is this not just equal to “text”?
>>> tuple(s)
('NL\r\n', 'CRLF\r\r\n', 'CR\rEOF') # Too many lines, butchered EOL sequence
>>> tuple(TextIOWrapper(BytesIO(text.encode("ascii")), "ascii", newline="\r\n"))
('NL\nCRLF\r\n', 'CR\rEOF') # This seems more reasonable
Although I have never had a use for newline="\r", it also seems broken:
>>> tuple(StringIO(text, newline="\r"))
('NL\r', 'CRLF\r', '\r', 'CR\r', 'EOF') # Way too many lines
>>> tuple(TextIOWrapper(BytesIO(text.encode("ascii")), "ascii", newline="\r"))
('NL\nCRLF\r', '\nCR\r', 'EOF')
The other newline options ("\n", "", and None) seem to behave correctly though.
There seem to be quite a few bug reports to do with newline translation in
StringIO, but I couldn’t see anything specifically about this one. However the
issue was mentioned at <https://bugs.python.org/issue20423#msg209581>.
I noticed there are test cases which appear to bless the current behaviour, as
seen in the patch for Issue 20498. IMO these tests are wrong.
----------
components: IO
messages: 226895
nosy: vadmium
priority: normal
severity: normal
status: open
title: Bizarre StringIO(newline="\r\n") translation
type: behavior
versions: Python 3.4
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue22413>
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