Python-сообщество

 from PyQt5 import QtCore, QtGui, QtWidgets
import sys
class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(661, 317)
        MainWindow.setStyleSheet("background-color: rgb(170, 170, 0);")
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.pushButton = QtWidgets.QPushButton(self.centralwidget)
        self.pushButton.setGeometry(QtCore.QRect(60, 70, 121, 31))
        self.pushButton.setStyleSheet("background-color: rgb(255, 85, 0);")
        self.pushButton.setObjectName("pushButton")
        self.label = QtWidgets.QLabel(self.centralwidget)
        self.label.setGeometry(QtCore.QRect(310, 80, 201, 31))
        self.label.setStyleSheet("background-color: rgb(0, 255, 255);")
        self.label.setText("")
        self.label.setObjectName("label")
        MainWindow.setCentralWidget(self.centralwidget)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)
        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)
    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
        self.pushButton.setText(_translate("MainWindow", "Выбрать"))
class Ui_Dialog(object):
    def setupUi(self, Dialog):
        Dialog.setObjectName("Dialog")
        Dialog.resize(400, 300)
        self.buttonBox = QtWidgets.QDialogButtonBox(Dialog)
        self.buttonBox.setGeometry(QtCore.QRect(30, 240, 341, 32))
        self.buttonBox.setOrientation(QtCore.Qt.Horizontal)
        self.buttonBox.setStandardButtons(QtWidgets.QDialogButtonBox.Cancel|QtWidgets.QDialogButtonBox.Ok)
        self.buttonBox.setObjectName("buttonBox")
        self.lineEdit = QtWidgets.QLineEdit(Dialog)
        self.lineEdit.setGeometry(QtCore.QRect(50, 30, 161, 31))
        self.lineEdit.setObjectName("lineEdit")
        self.retranslateUi(Dialog)
        self.buttonBox.accepted.connect(Dialog.accept)
        self.buttonBox.rejected.connect(Dialog.reject)
        QtCore.QMetaObject.connectSlotsByName(Dialog)
    def retranslateUi(self, Dialog):
        _translate = QtCore.QCoreApplication.translate
        Dialog.setWindowTitle(_translate("Dialog", "Dialog"))
class Proba_osn_win(QtWidgets.QMainWindow):
    def __init__(self):
        super(Proba_osn_win, self).__init__()
        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)
        self.ui.pushButton.clicked.connect(self.win_2_otkr)
    def win_2_otkr(self):
        self.application = Proba_win_2()
        result = self.application.exec()
        if result == QtWidgets.QDialog.Accepted:
            if self.application.znach.isdigit():
                self.ui.label.setText(self.application.znach)
            elif self.application.znach.count('.') == 1 and self.application.znach.replace('.', '').isdigit():
                self.ui.label.setText(str(float(self.application.znach) * 2))
            else:
                QtWidgets.QMessageBox.information(self, "ВНИМАНИЕ!", 'Вы ввели недопустимое значение!')
class Proba_win_2(QtWidgets.QDialog):
    def __init__(self):
        super(Proba_win_2, self).__init__()
        self.ui = Ui_Dialog()
        self.ui.setupUi(self)
        self.ui.lineEdit.textChanged[str].connect(self.vyb)
        self.ui.buttonBox.clicked.connect(self.accept)
    def vyb(self, item):
        self.znach = item
app = QtWidgets.QApplication([])
application = Proba_osn_win()
application.show()
sys.exit(app.exec())

         MainWindow.setStyleSheet("QMainWindow{background-color: rgb(170, 170, 0);}")