x = [1, 2, 8]
y = [4, 5]
def ret(x, y):
if len(x) == len(y):
return [f"{x[i]}/{y[i]}" for i in range(len(x))]
else:
t = y if len(x) > len(y) else x
z = t + [None]*(abs(len(x) - len(y)))
return [f"{x[i]}/{z[i]}" for i in range(len(x))]
print(ret(x, y), sep='\n')