from tkinter import *
class Aplication(Frame):
    def __init__(self, master):
        super(Aplication, self).__init__(master)
        self.grid()
        self.create_weget()
    def check(self):
        choose = self.list.curselection()
        if choose == "Test":
            print('I choosed Test')
        elif choose == "Test2":
            print('I choosed Test2')
        elif choose == "Test3":
            print('I choosed Test3')
        else:
            print('I choosed nothing')
 
    def create_weget(self):
        self.list = Listbox(self,height=5,width=15,selectmode=SINGLE)
        self.names = { 'Test', 'Test2', 'Test3'}
        for i in self.names:
            self.list.insert(END,i)
        self.list.grid(row = 0, column = 0)
        self.bttncheck = Button(self,text = 'Enter',command = self.check)
        self.bttncheck.grid()
root = Tk()
root.title("BY")
root.geometry("300x300")
root.resizable(False,False)
app = Aplication(root)
root.mainloop()