I have a list e.g. l1 = [1,2,3,4] and another list: l2 = [1,2,3,4,5,6,7,1,2,3,4]. I would like to check if l1 is a subset in l2 and if it is, then I want to delete these elements from l2 such that l2 would become [5,6,7,1,2,3,4], where indexes 0-3 have been removed.

Is there a pythonic way of doing this?

I tried this:

l1 = [1,2,3,4]
l2 = [1,2,3,4,5,6,7,1,2,3,4]
l3 = []
for i in l2:if i in l1:l3.append(i)
-> prints [5,6,7]

However I would like the output to be [5,6,7,1,2,3,4].

Well, here is a brute-force way. There are probably more efficient ways. If you expect to encounter a matching sublist early, the performance shouldn't be terrible.

>>> l1 = [1,2,3,4]
>>> l2 = [1,2,3,4,5,6,7,1,2,3,4]
>>> for i in range(0, len(l2), len(l1)):
...     if l2[i:len(l1)] == l1:
...         del l2[i:len(l1)]
...         break
...
>>> l1
[1, 2, 3, 4]
>>> l2
[5, 6, 7, 1, 2, 3, 4]
>>>

Or if you don't want to modify l2, you could do the following:

>>> l1 = [1,2,3,4]
>>> l2 = [1,2,3,4,5,6,7,1,2,3,4]
>>> for i in range(0, len(l2), len(l1)):
...     if l2[i:len(l1)] == l1:
...         break
...
>>> l2[:i] + l2[i+len(l1):]
[5, 6, 7, 1, 2, 3, 4]
>>>