[question]redirecting stdout to display via widget?

[fantagol]

Tks 1k wysota, for your answer, but if I change readOutput in

def readOutput(self):
        print self.process.readStdout()

def readOutput(self):
        print self.process.readStdout()

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I don't get any output too, and futher the process is not running,
according to QProcess.ProcessState = 0.

bye
Fantagol

[wysota]

When are you reading the state? Just after calling start()? If so then the process is not started yet at that point. Either way make sure you pass correct arguments to start(). To me it seems "python" is the name of your program and "test1.py" and "my_file.tex" are its arguments. Unless of course you do have an executable called "python test1.py" but that would be weird.

[fantagol]

Thanks very much for your precious help wysota, but nothing happens.This is what I did:

According to this Documentation

I add this connection

self.connect(self.process, QtCore.SIGNAL("started()"), self.processIsStarted)

self.connect(self.process, QtCore.SIGNAL("started()"), self.processIsStarted)

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add a new function:

def processIsStarted(self):
        print "according to SIGNAL STARTED() process with pid: ",str(self.process.pid()),"is started"
        print "Its State is ", self.process.ProcessState()

def processIsStarted(self):
        print "according to SIGNAL STARTED() process with pid: ",str(self.process.pid()),"is started"
        print "Its State is ", self.process.ProcessState()

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and change the calling:

def startCommand(self):        
        self.process.start("python", QtCore.QStringList(["test1.py","my_file.txt"]))
        StartString="Process started with pid: "+str(self.process.pid())
        print  StartString
        self.textBrowser.append(StartString)
        print self.process.ProcessState()
        self.startButton.setEnabled(False)
        self.stopButton.setEnabled(True)

def startCommand(self):        
        self.process.start("python", QtCore.QStringList(["test1.py","my_file.txt"]))
        StartString="Process started with pid: "+str(self.process.pid())
        print  StartString
        self.textBrowser.append(StartString)
        print self.process.ProcessState()
        self.startButton.setEnabled(False)
        self.stopButton.setEnabled(True)

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To starts a given program, i have to use this instantiation?

QProcess.start (self, QString program, QStringList arguments, QIODevice.OpenMode mode = QIODevice.ReadWrite)

QProcess.start (self, QString program, QStringList arguments, QIODevice.OpenMode mode = QIODevice.ReadWrite)

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Is QIODevice.OpenMode important?

tks to all
fantagol

[wysota]

No, the mode is not important for you. Does it work if you change test1.py to an absolute path? It is likely your file cannot be found. Although in this case python SHOULD start, it would just quit immediately. Unless your python binary cannot be found as well.

[fantagol]

Here the new files:
test1.py
CapturingOutputfromProcess.py

I think that the python script "test1.py" is started by my code, but self.process.ProcessState() say me quite another thing. I change the test1.py with a simple infinite print cycle:

#!/usr/bin/python
print "test1"
print "test2"
#from time import sleep
i=0
while 1:
    print i
    #sleep(1)
    if i == 5:
        #os.kill(os.getpid(),signal.SIGKILL)
        pass
    i +=1

#!/usr/bin/python
print "test1"
print "test2"
#from time import sleep
i=0
while 1:
    print i
    #sleep(1)
    if i == 5:
        #os.kill(os.getpid(),signal.SIGKILL)
        pass
    i +=1

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I think that the new process is started because i can see its pid on "System Monitor", and its cpu occupation. This is the new attemp in the script:

def startCommand(self):
        self.process.start("python", QtCore.QStringList(["/home/MyUserAccount/test1.py"]))
        StartString="Process started with pid: "+str(self.process.pid())
        print  StartString
        self.textBrowser.append(StartString)
        print self.process.ProcessState()
        #self.process.close()
        self.startButton.setEnabled(False)
        self.stopButton.setEnabled(True)
        #self.textBrowser.clear()
 
    def processIsStarted(self):
        print "according to SIGNAL STARTED() process with pid: ",self.process.pid()
 
    def stopCommand(self):
        print "Attempt to stop a process with Pid: ", str(self.process.pid())
        print "What is the State of this process?"
        print "Its State is ", self.process.ProcessState()
        self.resetButtons()
        print "Stop process, PID was: ", self.process.pid()
        os.kill(self.process.pid(), signal.SIGKILL)

def startCommand(self):
        self.process.start("python", QtCore.QStringList(["/home/MyUserAccount/test1.py"]))
        StartString="Process started with pid: "+str(self.process.pid())
        print  StartString
        self.textBrowser.append(StartString)
        print self.process.ProcessState()
        #self.process.close()
        self.startButton.setEnabled(False)
        self.stopButton.setEnabled(True)
        #self.textBrowser.clear()
        
    def processIsStarted(self):
        print "according to SIGNAL STARTED() process with pid: ",self.process.pid()
        
    def stopCommand(self):
        print "Attempt to stop a process with Pid: ", str(self.process.pid())
        print "What is the State of this process?"
        print "Its State is ", self.process.ProcessState()
        self.resetButtons()
        print "Stop process, PID was: ", self.process.pid()
        os.kill(self.process.pid(), signal.SIGKILL)

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When i run $python CapturingOutputfromProcess03.py , and press the button start, the message is shown correctly on the textbrowser "Process started with pid: 2277":

Process started with pid: 2277
0
according to SIGNAL STARTED() process with pid:  2277

Process started with pid: 2277
0
according to SIGNAL STARTED() process with pid:  2277

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A new pid appears on the System Monitor with its CPU occupation.
Then, when I press the stop button, the gui disappears and the terminal reveals this:

Attempt to stop a process with Pid:  2283
What is the State of this process?
Its State is  0
Stop process, PID was:  2283

Attempt to stop a process with Pid:  2283
What is the State of this process?
Its State is  0
Stop process, PID was:  2283

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I hope we can reach a solution.
Thanks a lot

[wysota]

But what's wrong exactly? It seems the script gets executed, what more do you want?

[fantagol]

But what's wrong exactly? It seems the script gets executed, what more do you want?

I want to redirect the standard output, and print on the textBrowser what comes from test1.py. I don't see anything append on the widget by test1.py.

[wysota]

Then connect to the appropriate signal and read the output from within the slot.

[fantagol]

I'm looking for the solution from many days!!
This is the SIGNAL:

self.connect(self.process, QtCore.SIGNAL("readyReadStdout()"), self.readOutput)
        self.connect(self.process, QtCore.SIGNAL("readyReadStderr()"), self.readErrors)

self.connect(self.process, QtCore.SIGNAL("readyReadStdout()"), self.readOutput)
        self.connect(self.process, QtCore.SIGNAL("readyReadStderr()"), self.readErrors)

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and this is the SLOT:

def readOutput(self):
        #print self.process.readStdout()
        self.textBrowser.append(QtGui.QString(self.process.readStdout()))
        #if self.process.isRunning()==False:
        #    self.textBrowser.append("\n Completed Successfully")
def readErrors(self):
        self.textBrowser.append("error: " + QtGui.QString(self.process.readLineStderr()))

def readOutput(self):
        #print self.process.readStdout()
        self.textBrowser.append(QtGui.QString(self.process.readStdout()))
        #if self.process.isRunning()==False:
        #    self.textBrowser.append("\n Completed Successfully")
def readErrors(self):
        self.textBrowser.append("error: " + QtGui.QString(self.process.readLineStderr()))

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....Where is the mistake?

[norobro]

As Wysota says:

connect to the appropriate signal

QProcess::readyReadStdout() is a PyQt3 signal. Check all of your functions against the doc that you linked in post #14.

[wysota]

....Where is the mistake?

The mistake is you are trying to use a signal that doesn't exist.

[fantagol]

Yeah.... i found the mistake this morning, The correct signals are:

readyReadStandardOutput()
readyReadStandardError()

readyReadStandardOutput()
readyReadStandardError()

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but now i read the text printed by test1.py only when the process is terminated.
I'd like to read line by line while it is running

[norobro]

A forum search yielded a similar thread.

For Python read the manual page: man python