Loop do not start for letter matching algoritm

[phob0s]

Finaly I solved my problem by doing this :

t = 0
tab = [0] * 26

if len(j1) < len(j2):
    n = len(j1)
else:
    n = len(j2)

for i in range(n):

    if j1[i] == j2[i]:
        t += 1
        tab[i] = t
        
    if tab[i] == 0:
            break

Because in my programm I need to stop the loop on minimum lenght.

Thank you.