import tkinter as tk

'''

One Spinbox automatically changes other Spinbox

'''

def sb1_changed(): # first spinbox

# get selection in first spinbox

selected = sb1_var.get()

# find its index on first list of all values

idx = vals1.index(selected)

# use index to get value for other list of all values

val = vals2[idx]

# set selection in second spinbox

sb2_var.set(val)

print('selected/index/val:', selected, idx, val)

def sb2_changed(): # second spinbox

# get selection in first spinbox

selected = sb2_var.get()

# find its index on first list of all values

idx = vals2.index(selected)

# use index to get value for other list of all values

val = vals1[idx]

# set selection in second spinbox

sb1_var.set(val)

print('selected/index/val:', selected, idx, val)

# ---

'''

sb1['textvariable'] give ID, not object but sb1.get() works

sb1['values'] gives list with values

'''

def changed(sb1, sb2):

# get selection in first spinbox

selected = sb1.get()

# find its index on first list of all values

idx = sb1['values'].index(selected) # <- but it works ['values']

# use index to get value for other list of all values

val = sb2['values'][idx] # <- but it works ['values']

print('selected/index/val:', selected, idx, val)

# set selection in second spinbox

sb2.insert('0', val) # <- problem with ['textvariable']

print('selected/index/val:', selected, idx, val)

# --- main ---

vals1 = ['A', 'B', 'C']

vals2 = ['1', '2', '3']

root = tk.Tk()

sb1_var = tk.StringVar()

sb2_var = tk.StringVar()

sb1 = tk.Spinbox(root, textvariable=sb1_var, values=vals1, command=sb1_changed)

sb1.pack()

sb2 = tk.Spinbox(root, textvariable=sb2_var, values=vals2, command=sb2_changed)

sb2.pack()

# ---

sbA_var = tk.StringVar()

sbB_var = tk.StringVar()

sbA = tk.Spinbox(root, textvariable=sbA_var, values=vals1)

sbA.pack()

sbB = tk.Spinbox(root, textvariable=sbB_var, values=vals2)

sbB.pack()

sbA['command'] = lambda:changed(sbA, sbB)

sbB['command'] = lambda:changed(sbB, sbA)

# ---

root.mainloop()