Vinay Sajip (Logging): A Qt GUI for logging

importdatetimeimportloggingimportrandomimportsysimporttime# Deal with minor differences between PySide2 and PyQt5try:fromPySide2importQtCore,QtGui,QtWidgetsSignal=QtCore.SignalSlot=QtCore.SlotexceptImportError:fromPyQt5importQtCore,QtGui,QtWidgetsSignal=QtCore.pyqtSignalSlot=QtCore.pyqtSlotlogger=logging.getLogger(__name__)## Signals need to be contained in a QObject or subclass in order to be correctly# initialized.#classSignaller(QtCore.QObject):signal=Signal(str,logging.LogRecord)## Output to a Qt GUI is only supposed to happen on the main thread. So, this# handler is designed to take a slot function which is set up to run in the main# thread. In this example, the function takes a string argument which is a# formatted log message, and the log record which generated it. The formatted# string is just a convenience - you could format a string for output any way# you like in the slot function itself.## You specify the slot function to do whatever GUI updates you want. The handler# doesn't know or care about specific UI elements.#classQtHandler(logging.Handler):def__init__(self,slotfunc,*args,**kwargs):super(QtHandler,self).__init__(*args,**kwargs)self.signaller=Signaller()self.signaller.signal.connect(slotfunc)defemit(self,record):s=self.format(record)self.signaller.signal.emit(s,record)## This example uses QThreads, which means that the threads at the Python level# are named something like "Dummy-1". The function below gets the Qt name of the# current thread.#defctname():returnQtCore.QThread.currentThread().objectName()## Used to generate random levels for logging.#LEVELS=(logging.DEBUG,logging.INFO,logging.WARNING,logging.ERROR,logging.CRITICAL)## This worker class represents work that is done in a thread separate to the# main thread. The way the thread is kicked off to do work is via a button press# that connects to a slot in the worker.## Because the default threadName value in the LogRecord isn't much use, we add# a qThreadName which contains the QThread name as computed above, and pass that# value in an "extra" dictionary which is used to update the LogRecord with the# QThread name.## This example worker just outputs messages sequentially, interspersed with# random delays of the order of a few seconds.#classWorker(QtCore.QObject):@Slot()defstart(self):extra={'qThreadName':ctname()}logger.debug('Started work',extra=extra)i=1# Let the thread run until interrupted. This allows reasonably clean# thread termination.whilenotQtCore.QThread.currentThread().isInterruptionRequested():delay=0.5+random.random()*2time.sleep(delay)level=random.choice(LEVELS)logger.log(level,'Message after delay of %3.1f: %d',delay,i,extra=extra)i+=1## Implement a simple UI for this cookbook example. This contains:## * A read-only text edit window which holds formatted log messages# * A button to start work and log stuff in a separate thread# * A button to log something from the main thread# * A button to clear the log window#classWindow(QtWidgets.QWidget):COLORS={logging.DEBUG:'black',logging.INFO:'blue',logging.WARNING:'orange',logging.ERROR:'red',logging.CRITICAL:'purple',}def__init__(self,app):super(Window,self).__init__()self.app=appself.textedit=te=QtWidgets.QPlainTextEdit(self)# Set whatever the default monospace font is for the platformf=QtGui.QFont('nosuchfont')f.setStyleHint(f.Monospace)te.setFont(f)te.setReadOnly(True)PB=QtWidgets.QPushButtonself.work_button=PB('Start background work',self)self.log_button=PB('Log a message at a random level',self)self.clear_button=PB('Clear log window',self)self.handler=h=QtHandler(self.update_status)# Remember to use qThreadName rather than threadName in the format string.fs='%(asctime)s %(qThreadName)-12s %(levelname)-8s %(message)s'formatter=logging.Formatter(fs)h.setFormatter(formatter)logger.addHandler(h)# Set up to terminate the QThread when we exitapp.aboutToQuit.connect(self.force_quit)# Lay out all the widgetslayout=QtWidgets.QVBoxLayout(self)layout.addWidget(te)layout.addWidget(self.work_button)layout.addWidget(self.log_button)layout.addWidget(self.clear_button)self.setFixedSize(900,400)# Connect the non-worker slots and signalsself.log_button.clicked.connect(self.manual_update)self.clear_button.clicked.connect(self.clear_display)# Start a new worker thread and connect the slots for the workerself.start_thread()self.work_button.clicked.connect(self.worker.start)# Once started, the button should be disabledself.work_button.clicked.connect(lambda:self.work_button.setEnabled(False))defstart_thread(self):self.worker=Worker()self.worker_thread=QtCore.QThread()self.worker.setObjectName('Worker')self.worker_thread.setObjectName('WorkerThread')# for qThreadNameself.worker.moveToThread(self.worker_thread)# This will start an event loop in the worker threadself.worker_thread.start()defkill_thread(self):# Just tell the worker to stop, then tell it to quit and wait for that# to happenself.worker_thread.requestInterruption()ifself.worker_thread.isRunning():self.worker_thread.quit()self.worker_thread.wait()else:print('worker has already exited.')defforce_quit(self):# For use when the window is closedifself.worker_thread.isRunning():self.kill_thread()# The functions below update the UI and run in the main thread because# that's where the slots are set up@Slot(str, logging.LogRecord)defupdate_status(self,status,record):color=self.COLORS.get(record.levelno,'black')s='<pre><font color="%s">%s</font></pre>'%(color,status)self.textedit.appendHtml(s)@Slot()defmanual_update(self):# This function uses the formatted message passed in, but also uses# information from the record to format the message in an appropriate# color according to its severity (level).level=random.choice(LEVELS)extra={'qThreadName':ctname()}logger.log(level,'Manually logged!',extra=extra)@Slot()defclear_display(self):self.textedit.clear()defmain():QtCore.QThread.currentThread().setObjectName('MainThread')logging.getLogger().setLevel(logging.DEBUG)app=QtWidgets.QApplication(sys.argv)example=Window(app)example.show()sys.exit(app.exec_())if__name__=='__main__':main()