не отображается comboBox

[Viktooor]

Не могу понять почему. Подскажите пожалуйста



import sys
from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *

class combodemo(QWidget):
def __init__(self, parent = None):
super(combodemo, self).__init__(parent)

self.cb = QComboBox()
self.setWindowTitle("combo box demo")
self.cb.setGeometry(20, 90, 70,20)
self.cb.addItems(["Сталь","Бронза","Алюминий"]) # I=0


def main():
app = QApplication(sys.argv)
ex = combodemo()
ex.show()
sys.exit(app.exec_())



if __name__ == '__main__':
main()

[Viktooor]

Отобразить spinBox
self.sp_D1 = QDoubleSpinBox(self,minimum =0,maximum=2000)
self.sp_D2 = QDoubleSpinBox(self,minimum =0,maximum=2000)
self.sp_D3 = QDoubleSpinBox(self,minimum =0,maximum=2000)
self.sp_L1 = QDoubleSpinBox(self,minimum =0,maximum=2000)

# Положение и размеры окна QDoubleSpinBox
self.sp_D1.setGeometry(610, 10, 70,20)
self.sp_D2.setGeometry(610, 30, 70,20)
self.sp_D3.setGeometry(610, 50, 70,20)
self.sp_L1.setGeometry(610, 70, 70,20)

self.sp_D1.valueChanged.connect(sel f.valuechange_D1)
self.sp_D2.valueChanged.connect(sel f.valuechange_D2)
self.sp_D3.valueChanged.connect(sel f.valuechange_D3)
self.sp_L1.valueChanged.connect(sel f.valuechange_L1)

def valuechange_D1(self):
D1 = self.sp_D1.value()
print("D1 =",D1)
def valuechange_D2(self):
D2 = self.sp_D2.value()
print("D2 = ",D2)
def valuechange_D3(self):
D3 = self.sp_D3.value()
print("D3 = ",D3)
def valuechange_L1(self):
L1 = self.sp_L1.value()
print("L1 = ",L1)
#------------------------------------------------------------------
self.cmb_1 = QtWidgets.QComboBox(self)
self.cmb_1.setGeometry(610, 90, 70,20)
self.cmb_1.addItems(["Сталь","Бронза","Алюминий"]) # I=0

#-----------------------------------------------------------------