class Login(QDialog):
def __init__(self, parent=None):

    self.contributors=['','A','B','C']
    super(Login, self).__init__(parent)
    self.nameLabel=QLabel(self)
    self.nameLabel.setText("Select Your name")
    self.nameLabel.setAlignment(Qt.AlignHCenter)
    self.cb=QComboBox(self)
    self.cb.setGeometry(QRect(40,40,491, 31))
    self.cb.setObjectName(("comboBox"))
    self.cb.addItems(self.contributors)
    self.cb.currentIndexChanged.connect(self.getEditor)
    self.buttonLogin = QPushButton('Login', self)
    self.buttonLogin.clicked.connect(self.close)
    layout = QVBoxLayout(self)
    layout.addWidget(self.nameLabel)
    layout.addWidget(self.cb)
    layout.addWidget(self.buttonLogin)
    self.resize(600,150)
    self.exec_()

def getEditor(self):
    text=str(self.cb.currentText())
    return text

if __name__ == '__main__':
    app = QApplication(sys.argv)
    login=Login()