pyqt4 gui application don't run

Question

I used the PyQt4 designer to design my GUI application, then I converted the .ui file to .py file. I tried to run the .py file but no window opened.

What is the problem with the .py file?

from PyQt4 import QtCore, QtGui

try:
    _fromUtf8 = QtCore.QString.fromUtf8
except AttributeError:
    def _fromUtf8(s):
        return s

try:
    _encoding = QtGui.QApplication.UnicodeUTF8


    def _translate(context, text, disambig):
        return QtGui.QApplication.translate(context, text, disambig, _encoding)
except AttributeError:
    def _translate(context, text, disambig):
        return QtGui.QApplication.translate(context, text, disambig)


class Ui_MainWindow(QtGui.QMainWindow):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName(_fromUtf8("MainWindow"))
        MainWindow.resize(460, 260)
        MainWindow.setMinimumSize(QtCore.QSize(460, 260))
        MainWindow.setMaximumSize(QtCore.QSize(460, 260))
        MainWindow.setBaseSize(QtCore.QSize(300, 100))
        self.centralwidget = QtGui.QWidget(MainWindow)
        self.centralwidget.setObjectName(_fromUtf8("centralwidget"))
        self.gridLayoutWidget = QtGui.QWidget(self.centralwidget)
        self.gridLayoutWidget.setGeometry(QtCore.QRect(0, 0, 451, 234))
        self.gridLayoutWidget.setObjectName(_fromUtf8("gridLayoutWidget"))
        self.gridLayout = QtGui.QGridLayout(self.gridLayoutWidget)
        self.gridLayout.setContentsMargins(-1, 5, -1, -1)
        self.gridLayout.setObjectName(_fromUtf8("gridLayout"))
        self.textBrowser = QtGui.QTextBrowser(self.gridLayoutWidget)
        self.textBrowser.setObjectName(_fromUtf8("textBrowser"))
        self.gridLayout.addWidget(self.textBrowser, 3, 2, 1, 1)
        self.pushButton_2 = QtGui.QPushButton(self.gridLayoutWidget)
        self.pushButton_2.setFlat(False)
        self.pushButton_2.setObjectName(_fromUtf8("pushButton_2"))
        self.gridLayout.addWidget(self.pushButton_2, 4, 2, 1, 1)
        self.label_3 = QtGui.QLabel(self.gridLayoutWidget)
        self.label_3.setIndent(5)
        self.label_3.setObjectName(_fromUtf8("label_3"))
        self.gridLayout.addWidget(self.label_3, 2, 0, 1, 1)
        self.lineEdit = QtGui.QLineEdit(self.gridLayoutWidget)
        self.lineEdit.setObjectName(_fromUtf8("lineEdit"))
        self.gridLayout.addWidget(self.lineEdit, 0, 2, 1, 1)
        self.label = QtGui.QLabel(self.gridLayoutWidget)
        self.label.setIndent(5)
        self.label.setObjectName(_fromUtf8("label"))
        self.gridLayout.addWidget(self.label, 0, 0, 1, 1)
        self.label_2 = QtGui.QLabel(self.gridLayoutWidget)
        self.label_2.setIndent(5)
        self.label_2.setObjectName(_fromUtf8("label_2"))
        self.gridLayout.addWidget(self.label_2, 1, 0, 1, 1)
        self.lineEdit_2 = QtGui.QLineEdit(self.gridLayoutWidget)
        self.lineEdit_2.setObjectName(_fromUtf8("lineEdit_2"))
        self.gridLayout.addWidget(self.lineEdit_2, 1, 2, 1, 1)
        self.pushButton = QtGui.QPushButton(self.gridLayoutWidget)
        self.pushButton.setObjectName(_fromUtf8("pushButton"))
        self.gridLayout.addWidget(self.pushButton, 1, 3, 1, 1)
        self.lineEdit_3 = QtGui.QLineEdit(self.gridLayoutWidget)
        self.lineEdit_3.setObjectName(_fromUtf8("lineEdit_3"))
        self.gridLayout.addWidget(self.lineEdit_3, 2, 2, 1, 1)
        self.pushButton_3 = QtGui.QPushButton(self.gridLayoutWidget)
        self.pushButton_3.setObjectName(_fromUtf8("pushButton_3"))
        self.gridLayout.addWidget(self.pushButton_3, 2, 3, 1, 1)
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtGui.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 460, 21))
        self.menubar.setObjectName(_fromUtf8("menubar"))
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtGui.QStatusBar(MainWindow)
        self.statusbar.setObjectName(_fromUtf8("statusbar"))
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        MainWindow.setWindowTitle(_translate("MainWindow", "Email Find", None))
        self.pushButton_2.setText(_translate("MainWindow", "Find", None))
        self.label_3.setText(_translate("MainWindow", "Emails File", None))
        self.label.setText(_translate("MainWindow", "URL", None))
        self.label_2.setText(_translate("MainWindow", "File", None))
        self.pushButton.setText(_translate("MainWindow", "Browse", None))
        self.pushButton_3.setText(_translate("MainWindow", "Browse", None))

Answer 1

pyuic4 (similarly to the regular Qt uic ) doesn't give you a file that you straight run to get a window, it just generates a class that builds the "UI content" of a MainWindow (or other window-like type) that you'll inherit to add your own stuff; the idea is that you want to do your own customization to the window (event handlers and the like), while delegating to this auxiliary class the "boring" part of building the designer-drawn UI.

Let's say pyuic4 generated your ui_mainwindow.py file; in your mainwindow.py you'll have something like:

import sys
from ui_mainwindow import Ui_MainWindow
from PyQt4.QtGui import QApplication

class MainWindow(Ui_MainWindow):
    def __init__(self, parent = None):
        Ui_MainWindow.__init__(self, parent)
        self.setupUi(self)
        # add your event handlers, extra code, ...

if __name__ == '__main__':
    app = QApplication(sys.argv)
    mw = MainWindow()
    mw.show()
    app.exec_()