Why calling remove method on the master list doesn't remove all the elements?

Just checked the other post and had this issue figured out. Basically when your removal iteration starts, the most-left item will be removed, creating a new indexing for the list, which creates problem for the on-going loop order.

Assume this is your original list,

list = ["1", "2", "3", "4", "5"]

and what happens when your loop starts is: list.remove([0]), hence your list become:

list = ["2", "3", "4", "5"]

but then the loop does not stop, it will do: list.remove([1]) to the code above, hence your list become:

list = ["2", "4", "5"]

but then the loop still does not stop, it will do: list.remove([2]) to the code above, hence your list become:

list = ["2", "4"]

then the loop still still does not stop, it will do: list.remove([3]) to the code above, which your list does not have anymore, hence your list stays the same and the loop ends:

list = ["2", "4"]

My first time answering question in the forum, hope it's helpful.

When you modify an iterator by removing items while it is being used to control a loop, it throws off the internal loop mechanisms and causes items to be skipped over. Similarly, if you were to add items instead, it could cause some items to be used twice.

Using a copy of the item as the iterator prevents this issue.