Combobox

import tkinter as tk
from tkinter import ttk
 
app = tk.Tk()
app.geometry('500x400+400+200')
backgroundColor = "#001"
app.title("Russian City")
app.configure(background= backgroundColor)
 
labelTop = tk.Label(app,text="Города России: ")
labelTop.place(x=180,y=10)
backgroundColor1 = "#001"
labelTop.configure(background= backgroundColor1, foreground="#ccc", font="13")
comboExample = ttk.Combobox(app,
                            values=["Абаза","Абакан","Абдулино","Апрелевка"],
                            state="readonly")
comboExample.place(x=180,y=40)
comboExample.current(0)
 
print(comboExample.current(), comboExample.get())
 
app.mainloop()

self.combo = QtWidgets.QComboBox(self)
self.combo.addItems(["CATERPILLAR","CUMMINS","DAVID_BROWN",
                        "DEUTZ","FORD","HANOMAG","IHC","ISUZU",
                        "IVECO_NEF-NEW_HOLLAND","JCB","JOHN_DEERE",
                        "KOMATSU","KUBOTA","LEYLAND","LIEBHERR",
                        "MITSUBISHI","MWM","PERKINS","SHANGHAL_DIESEL",
                        "VOLVO","YANMAR","ФИЛЬТРЫ"
                        ])
self.combo.setGeometry(10,20,350,30)
 
button = QtWidgets.QPushButton("Запуск",self)
button.setGeometry(85,80,200,40)
button.clicked.connect(self.on_button)
 
def on_button(self):
        category = self.combo.currentText()
        #print(cat)
 
        if category == 'CATERPILLAR':
            print('asw')
        elif category == 'CUMMINS':
            print('dfgdgf')

self.combo.activated[str].connect(self.onActivated)
def onActivated(self, index):
        self.combo = index
        #print(self.combo)