Upon closer
inspection, it appears that the stdout from 7z isn't returned to the
calling process until the archiving operation has finished.
Therefore, PyQt4 is probably not to blame for the below scenario. If
these new findings are incorrect, I'll post another message once I've
received confirmation.
Chris Giles wrote, On 24/09/06 18:27:
Dear PyKDE Members
I'm opening a new QThread which launches a command-line archiver (7z)
in a QProcess (called 'pArc').
I'm using following code block within that thread:
while not
pArc.waitForFinished(250) :
if
pArc.waitForReadyRead(100) :
sArcData = QtCore.QString(pArc.readData(512))
print
"Output = " + str(sArcData)
else :
print
"Nothing"
While the (large) files are being archived, "Nothing" is printed to the
screen several times. When the process is finished, "Output = ..." is
then printed. However, I know that 7z prints data to its stdout while
the archiving process is happening (i.e. it doesn't just wait until it
has finished). I want to update a QProgressBar based on the output
from 7z, so I can't wait until it has finished otherwise this defeats
the purpose of the QProgressBar.
The
PyQt4 documentation has this to say:
You also
have the option of forwarding the output of the running process to the calling, main
process, by passing ForwardedChannels as the argument.
QProcess.ForwardedChannels:
QProcess forwards the output of the running process onto the main
process. Anything the child process writes to its standard output and
standard error will be written to the standard output and standard error
of the main process.
So, I then added
this
line before the above code block:
pArc.setReadChannelMode(QtCore.QProcess.ForwardedChannels)
While the file is being archived, I can now correctly see the standard
output being progressively printed to the screen. But how do I read
this output since it is no longer associated with my QProcess? How do I access the standard
output of this 'main' process?
Thanks for your help.
Chris
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