[This post cross-posed to https://forum.qt.io/topic/85493/unicodedecodeerror-with-output-from-windows-os-command/18 ]
For the record, I have done exhaustive investigation, and there is only one solution which "correctly" displays the £ character under Windows. I am exhausted so will keep this brief:
To create a file name with a £ in it: Go into, say, Notepad and use its Save to name a file like abc£.txt. This is in the UK, using a UK keyboard and a standard UK-configured Windows.
Note that at this point if you view the filename in either Explorer or, say, via dir you do see a £, not some other character. That's what my user will want to see in the output of the command he will run.
Run an OS command like robocopy or even dir, which will include the filename in its output.
Read the output with QProcess.readAllStandardOutput(). I'm saying the £ character will arrive as a single byte of value 0x9c.
For the required Python/PyQt decoding bytes->str (QByteArray->QString) line, the only thing which works (does not raise an exception) AND represents the character as a £ is: ba.bytes().decode("cp850").
That is the "Code Page 850", used in UK/Western Europe (so I'm told). It is the result output of you open a Command Prompt and execute just chcp.
Any other decoding either raises UnicodeDecodeError (e.g. if utf-8) or decodes but represents it with another character (e.g. if windows_1252 or cp1252).
I still haven't found a way of getting that cp850 encoding name programatically from anywhere --- if you ask Python for, say, the "system encoding" or "user's preferred encoding" you get the cp1252 --- so I've had to hard-code it. [EDIT: If you want it, it's ctypes.cdll.kernel32.GetConsoleOutputCP().]
So there you are. I don't have C++ as opposed to Python for Qt, but I have a suspicion that if anyone tries it using the straight C++ Qt way of text = QString(process.readAllStandardOutput()) they'll find they do not actually get to see the £ symbol....
