def replace_all_sublists(lst, old, new):
result = []
i = 0
n = len(old)
while i < len(lst):
if lst[i:i+n] == old:
result.extend(new)
i += n
else:
result.append(lst[i])
i += 1
return result
lst = [1, 2, 3, 4, 7, 3, 4, 5]
print(replace_all_sublists(lst, [3, 4], ["x", "y"]))
'''
run:
[1, 2, 'x', 'y', 7, 'x', 'y', 5]
'''