How to add a drop down menu and return the selected option

Post the code you have so far along with any problems.

use GUI toolkit. If you go for wxPython there is wxComboBox as one of options

You can use Tkinter that comes with the Python installation:

# using Tkinter's Optionmenu() as a combobox

try:
    # Python2
    import Tkinter as tk
except ImportError:
    # Python3
    import tkinter as tk

def select():
    sf = "value is %s" % var.get()
    root.title(sf)
    # optional
    color = var.get()
    root['bg'] = color


root = tk.Tk()
# use width x height + x_offset + y_offset (no spaces!)
root.geometry("%dx%d+%d+%d" % (330, 80, 200, 150))
root.title("tk.Optionmenu as combobox")

var = tk.StringVar(root)
# initial value
var.set('red')

choices = ['red', 'green', 'blue', 'yellow','white', 'magenta']
option = tk.OptionMenu(root, var, *choices)
option.pack(side='left', padx=10, pady=10)

button = tk.Button(root, text="check value slected", command=select)
button.pack(side='left', padx=20, pady=10)

root.mainloop()

simple wxPyCode that does nothing, just a display!
import wx

class wxDemo(wx.Frame):
    def __init__(self, parent): 
        wx.Frame.__init__(self, parent, title='Demo Frame')
        self.panel = wx.Panel(self, -1)
        self.sizer = wx.BoxSizer(wx.VERTICAL)
        self.combo = wx.ComboBox(self.panel, choices=['Moja', 'Mbili', 'Tatu', 'Nne', 'Tano'])
        self.text = wx.TextCtrl(self.panel, wx.ID_ANY, style=wx.TE_MULTILINE)
        
        self.sizer.Add(self.combo, 0, wx.EXPAND)
        self.sizer.Add(self.text, 1, wx.EXPAND)
        
        self.panel.SetSizer(self.sizer)
        self.panel.Layout()
        
app = wx.App()
fr = wxDemo(None)
fr.Show()
app.MainLoop()