class Solution:
    def deleteDuplicates(self, head):
        # so I dont lose my original head, I set a variable current
        current = head
        # traverse through LL, ensuring curr and curr.next exist
        while current and current.next is not None:
            # prev becomes the value to which we compare other values to
            prev = current
            current = current.next
            # we move current until current.val no longer matches prev value
            # ensure we don't hit None by checking that current also exists
            while current and prev.val == current.val:
                current = current.next
            # whether current is now None or some number that is not prev.val, we set prev.next
            prev.next = current
        return head

This also seems like an O(n) solution.