Redirect both stdin and stdout of a process to a PyQt text edit.

redirect.py

from PyQt4 import QtGui, QtCore, uic

def p(x):
    print x

class MainWindow(QtGui.QMainWindow):
    def __init__(self):
        QtGui.QWidget.__init__(self)
        uic.loadUi('redirect.ui', self)

        print 'Connecting process'
        self.process = QtCore.QProcess(self)
        self.process.readyReadStandardOutput.connect(self.stdoutReady)
        self.process.readyReadStandardError.connect(self.stderrReady)
        self.process.started.connect(lambda: p('Started!'))
        self.process.finished.connect(lambda: p('Finished!'))

        print 'Starting process'
        self.process.start('python', ['speak.py'])

    def append(self, text):
        cursor = self.textEdit.textCursor()
        cursor.movePosition(cursor.End)
        cursor.insertText(text)
        #self.output.ensureCursorVisible()

    def stdoutReady(self):
        text = str(self.process.readAllStandardOutput())
        print text.strip()
        self.append(text)

    def stderrReady(self):
        text = str(self.process.readAllStandardError())
        print text.strip()
        self.append(text)


def main():
    import sys
    app = QtGui.QApplication(sys.argv)
    win = MainWindow()
    win.show()
    sys.exit(app.exec_())
    
if __name__ == '__main__':
    main()

redirect.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>800</width>
    <height>600</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <layout class="QVBoxLayout" name="verticalLayout">
    <item>
     <widget class="QTextEdit" name="textEdit">
      <property name="font">
       <font>
        <pointsize>12</pointsize>
       </font>
      </property>
      <property name="readOnly">
       <bool>true</bool>
      </property>
     </widget>
    </item>
   </layout>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <resources/>
 <connections/>
</ui>

speak.py

from time import sleep
from random import randrange, choice
from sys import stderr, stdout

def main():
    options = 2 * ['good'] + ['bad']
    with open('log.txt', 'w') as f:
        for i in range(10):
            sleep(randrange(1, 3))
            option = choice(options)
            if option == 'good':
                stdout.write('good\n')
                stdout.flush()
            else:
                stderr.write('bad\n')
                stderr.flush()
            f.write(option + '\n')
            f.flush()

if __name__ == '__main__':
    main()