Convert string to int

[Frankduc]

Hello,

Trying to sum string numbers to int, but there is a ; between them.

tab = input("Éntrez les nombres entiers séparés par des (;) : ")

list_nb= [tab]
list_nb = [item.replace(";"," ") for item in list_nb]

nbs = list(map(int, list_nb))

somme = 0
for nb in nbs:
    print((somme + nb)/len(nbs))
    

Error:
Éntrez les nombres entiers séparés par des (;) : 4;5;7;
Traceback (most recent call last):
  File "<string>", line 10, in <module>
ValueError: invalid literal for int() with base 10: '4 5 7 '
> 

Why i get this error. Numbers need to be input with ";"

Thank you