Python Qt4 - part 004.

Another tutorial about PyQt4 with QLCDNumber widget displays a number with LCD-like digits.
This tutorial will show you how to deal with this widget.
First, you need to know more about QLCDNumber, so take a look here.
The first example is very simple and will show just one digit, see:

import sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *

class Digit(QWidget):

    def __init__(self, parent=None):
        QWidget.__init__(self, parent)
        self.setWindowTitle("One digit")
        lcd = QLCDNumber(self)

app = QApplication(sys.argv)
ls = Digit()
ls.show()
sys.exit(app.exec_())

Now, the next step is to send data to this digit.
One good example is with one slider.
The position of the slider will be send to the QLCDNumber.
How can do that? Will need a vbox to put the QLCDNumber and the slider and then using signal and slot.
Let's see the example:

import sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *
class Digit(QWidget):

    def __init__(self, parent=None):
        QWidget.__init__(self, parent)
        #make widgets
        self.setWindowTitle("One digit with slider")
        lcd = QLCDNumber(self)
        slider = QSlider(Qt.Horizontal, self)
        #set layout variable vbox
        vbox = QVBoxLayout()
        #add widgests
        vbox.addWidget(lcd)
        vbox.addWidget(slider)
        #set the vbox to layout
        self.setLayout(vbox)
        #create signal to slot
        self.connect(slider, SIGNAL("valueChanged(int)"),lcd, SLOT("display(int)"))
        self.resize(200, 170)
if __name__ == '__main__':
    app = QApplication(sys.argv)
    ls = Digit()
    ls.show()
    sys.exit(app.exec_())

In the source code in the example, you can see the comments that mark the steps of creating and executing the python script.
Let's try another example with a digital clock:

import sys
from PyQt4 import QtCore, QtGui

class digital_clock(QtGui.QLCDNumber):
    def __init__(self, parent=None):
        super(digital_clock, self).__init__(parent)
        self.setSegmentStyle(QtGui.QLCDNumber.Filled)
        #the defaul is 5 , change to 8 for seconds
        self.setDigitCount(5)
        self.setWindowTitle("Digital Clock")
        self.resize(200, 70)
        timer = QtCore.QTimer(self)
        timer.timeout.connect(self.showTime)
        timer.start(1000)
        self.showTime()

    def showTime(self):
        time = QtCore.QTime.currentTime()
        text = time.toString('hh:mm')
        #if you setDigitsCount to 8
        #uncomment the next line of code
        #text = time.toString('hh:mm:ss')
        if (time.second() % 2) == 0:
            text = text[:2] + ' ' + text[3:]
        self.display(text)

if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    clock = digital_clock()
    clock.show()
    sys.exit(app.exec_())

If you want to see seconds, then you need to set the digit count of the LCD to 8 ( it's 5 by default) of setDigitCount.
Also you need to uncomment this line of code: text = time.toString('hh:mm:ss') and comment the old one.
You can solve multiple issues with this widget, like: stopwatch, timer, clock down timer ...

Python Qt4 - part 003.

Today I've taken a simple example with PyQt4 compared to the other tutorials we have done so far.
The main reason was to understand and use PyQt4 to display an important message.
To make this example I have set the following steps for my python program.

• importing python modules
• creating the application in PyQt4 as a tray icon class
• establishing an exit from the application
• setting up a message to display
• display the message over a period of time
• closing the application
• running the python application

Let's see my source code of my python application:

#! /usr/bin/env python
import sys
from PyQt4 import QtGui, QtCore

class SystemTrayIcon(QtGui.QSystemTrayIcon):
    def __init__(self, parent=None):
        QtGui.QSystemTrayIcon.__init__(self, parent)
        self.setIcon(QtGui.QIcon("mess.svg"))
        menu = QtGui.QMenu(parent)
        exitAction = menu.addAction("Exit")
        self.setContextMenu(menu)
        QtCore.QObject.connect(exitAction,QtCore.SIGNAL('triggered()'), self.exit)

    def click_trap(self, value):
        if value == self.Trigger: #left click!
            self.left_menu.exec_(QtGui.QCursor.pos())

    def welcome(self):
        self.showMessage("Hello user!", "This is a message from PyQT4")

    def show(self):
        QtGui.QSystemTrayIcon.show(self)
        QtCore.QTimer.singleShot(600, self.welcome)

    def exit(self):
        QtCore.QCoreApplication.exit()

def main():
    app = QtGui.QApplication([])
    tray = SystemTrayIcon()
    tray.show()
    app.exec_()

if __name__ == '__main__':
    main()

I used PyQt4 python module to make the application and sys python module for exit from application.
About running application: the main function will run the application.
The python class SystemTrayIcon will work only if we used QApplication to make like any application.
This is the reason I used the variable app.
The tray variable is used to run it like tray icon application.
Into the SystemTrayIcon class, I put some functions to help me with my issue.
Under __init__ I used all settings for my tray icon application: the icon, the exit menu, signal for the exit.
The next functions come with:

• click_trap - take the click of the user ;
• welcome - make a message to display;
• show - display the welcome message;
• exit - exit from the application

The result of my python script is this message:

About the showMessage then this helps you:

QSystemTrayIcon.showMessage (self, QString title, QString msg, MessageIcon icon = QSystemTrayIcon.Information, int msecs = 10000)

Shows a balloon message for the entry with the given title, message and icon for the time specified in millisecondsTimeoutHint. title and message must be plain text strings.
The message can be clicked by the user; the messageClicked() signal will be emitted when this occurs.
Note that the display of messages is dependent on the system configuration and user preferences and that messages may not appear at all. Hence, it should not be relied upon as the sole means for providing critical information.
On Windows, the millisecondsTimeoutHint is usually ignored by the system when the application has focus.
On Mac OS X, the Growl notification system must be installed for this function to display messages.
This function was introduced in Qt 4.3.