I have this code:
import tkinter as tk
from tkinter import ttk
root = tk.Tk()
# Select Country Dropdown Menu
frame_country = tk.Frame(root, highlightbackground="black", highlightthickness=1)
frame_country.grid(row=0, column=0, pady=(0,5), sticky="nsew")
label_country_dropdown = ttk.Label(frame_country, text="Country:")
label_country_dropdown.grid(row=0, column=0, sticky="w")
dropdown_country = ttk.Combobox(frame_country)
dropdown_country.grid(row=0, column=1, sticky="e")
countriesList = ["Spain", "Romania"]
dropdown_country["values"] = countriesList
# Select Municipality Dropdown Menu
frame_municipality = tk.Frame(root, highlightbackground="black", highlightthickness=1)
frame_municipality.grid(row=1, column=0, sticky='nsew')
label_municipality_dropdown = ttk.Label(frame_municipality, text="Municipality:")
label_municipality_dropdown.grid(row=1, column=0, sticky="w")
dropdown_municipality = ttk.Combobox(frame_municipality)
dropdown_municipality.grid(row=1, column=1, sticky="e")
municipalitiesList = ["Madrid", "Bucarest"]
dropdown_municipality["values"] = municipalitiesList
root.mainloop()
That produces this result:
The country dropdown menu is not aligned to the right although I used sticky="e".
If I change "Municipality" to "Foo" the result is the oposite:
Probably any widget is well aligned.

