I import another Python module in my pyqt code file to get inputs and show output. but it gives me error 

> 
> QWidget: Must construct a QApplication before a QPaintDevice
> 
> 
> 

My code is:

```
from PyQt4 import QtGui
import sys
from untitled import Ui_MainWindow
from PyQt4.QtCore import SIGNAL
from PyQt4.QtGui import QDialog, QApplication, QPushButton, QLineEdit, QFormLayout
from naivebase import *

class Main (QtGui.QMainWindow):
    def __init__(self):
        QtGui.QMainWindow.__init__(self)
        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)
        self.ui.pushButton.clicked.connect(self.pushButton_clicked)
        self.ui.lineEdit.returnPressed.connect(self.pushButton_clicked)
        # self.connect(QPushButton(), SIGNAL("clicked()"),  self.pushButton_clicked)

    def pushButton_clicked(self):
         text1 = self.ui.lineEdit.text()
         # print text1
         ob2 = TweetClassfier()
         txt = ob2.lbl1
         self.ui.label_2.setText(txt)

if __name__ == "__main__":
    app = QtGui.QApplication(sys.argv)
    window = Main()
    window.show()
    sys.exit(app.exec_())

```

I have debugged the code it gives me this error after this line 

```
QtGui.QMainWindow.__init__(self)

```