Thanks MRAB, your solution works a treat.
I'm replying to the list so others can know that this solution works.
Note that sys.stderr.detach() is only available in >= 3.1, so one might
need to do some version checking to get it to work properly in both
versions. It also can mess up with the buffering and therefore the order
of the output of stderr vs stdout.
Thanks again.
Peter
On 20/10/2017 10:19 AM, MRAB wrote:
On 2017-10-19 22:46, Peter via Python-list wrote:
I came across this code in Google cpplint.py, a Python script for
linting C++ code. I was getting funny results with Python 3.6.3, but it
worked fine under 2.7.13
I've tracked the problem to an issue with StreamReaderWriter; the
traceback and error never shows under 3. The _cause_ of the error is
clear (xrange not in Py3), but I need the raised exception to show.
I'm running Python 3.6.3 32bit on Windows 10. I also get the same
results on Python 3.5.2 on Ubuntu (under WSL)
I'm not super familiar with rebinding stderr with codecs, but I'm
guessing they are doing it because of some Unicode issue they may have
been having.
I have a workaround - drop the rebinding - but it seems like there might
be an error in StreamReaderWriter.
Do other people see the same behaviour?
Is there something I'm not seeing or understanding?
Would I raise it on issue tracker?
Peter
----------------------------------------------------------
import sys
import codecs
sys.stderr = codecs.StreamReaderWriter(
sys.stderr, codecs.getreader('utf8'), codecs.getwriter('utf8'),
'replace')
# This should work fine in Py 2, but raise an exception in Py3
# But instead Py3 "swallows" the exception and it is never seen
print(xrange(1, 10))
# Although this line doesn't show in Py 3 (as the script has silently
crashed)
print("This line doesn't show in Py 3")
----------------------------------------------------------
StreamReaderWriter is being passed an encoder which returns bytes
(UTF-8), but the output stream that is being passed, to which it will
be writing those butes, i.e. the original sys.stderr, expects str.
I'd get the underlying byte stream of stderr using .detach():
sys.stderr = codecs.StreamReaderWriter(sys.stderr.detach(),
codecs.getreader('utf8'), codecs.getwriter('utf8'), 'replace')
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