exemplo.py

from tkinter import ttk
from ttkthemes import ThemedTk

# Crio a janela e acrescento o tema Ubuntu
root = ThemedTk(theme = 'ubuntu')

# Crio o button já estilizado..
ttk.Button(root, text = 'Quit', command = root.destroy).pack(padx = '40', pady = '60')

root.title('Teste de tema!')
root.config(background = 'white')
root.geometry('200x200')
root.resizable(False, False)
root.eval('tk::PlaceWindow . center')
root.mainloop()