Creating the application's framework

Start by creating a folder to hold your application's source code, and move the data folder you created earlier into it. Next, we want to create the basic framework for our application using the techniques we learned in Chapter 1, Getting Started with QGIS. Create a module named lex.py, and enter the following into this file:

import os, os.path, sys

from qgis.core import *
from qgis.gui import *
from PyQt4.QtGui import *
from PyQt4.QtCore import *

class MapExplorer(QMainWindow):
    def __init__(self):
        QMainWindow.__init__(self)
        self.setWindowTitle("Landmark Explorer")
        self.resize(800, 400)

def main():
    QgsApplication.setPrefixPath(os.environ['QGIS_PREFIX'], True)
    QgsApplication.initQgis()

    app = QApplication(sys.argv)

    window = MapExplorer()
    window.show()
    window.raise_()

    app.exec_()
    app.deleteLater()
    QgsApplication.exitQgis()

if __name__ == "__main__":
    main()

We're simply importing the...