How do I make a copy of a list without changing its contents?

Question

However, when I change new, it changes self._marker as well. I want to be able to change new, without it changing self._marker. I cannot use deepcopy either, since I do this operation several thousand times, and incur a huge performance penalty for using deepcopy.

What do I do?

Answer 1

You are on the right track, but your proposed solution does not work because you do not make a copy of the inner lists. They stay the same.

You can do this:

new_list = [e[:] for e in self._marker]

This performa a deepcopy which is what you need in that case.

This answers the question you asked. If you have other requirements, you need to make them explicit in your question.