from tkinter import *
selection_window = Tk()
selection_window.wm_title("")
selection_window.geometry('{}x{}'.format(200, 150))
frame_1 = Frame(selection_window, width=200, height=30)
Button(frame_1, text="Single",height = 100).pack(side=LEFT,anchor=S)
Button(frame_1,text="Range",command=Toplevel,height = 20).pack(side=RIGHT,anchor=S)
frame_1.pack()
selection_window.mainloop()

from tkinter import *
selection_window = Tk()
selection_window.wm_title("")
selection_window.geometry('{}x{}'.format(200, 150))
frame_1 = Frame(selection_window, width=200, height=30)
frame_1.pack()
Button(frame_1, text="Single",height = 10).pack(side=LEFT, anchor=S, padx=[0,40])
Button(frame_1,text="Range",command=Toplevel,height = 2).pack(side=RIGHT, anchor=S, padx=[20,0])
selection_window.mainloop()

from tkinter import *
import tkinter.ttk as ttk
s=ttk.Style()
print('Style themes on my system are ', s.theme_names())
s.theme_use('clam')
s.configure('bb.TButton', background='white', padding=50)
b1=ttk.Button(text='Default')
b1.pack(side=LEFT, anchor=S, padx=[0,40])
b2=ttk.Button(text='Custom', style='bb.TButton')
b2.pack(side=RIGHT, anchor=S, padx=[20,0])