Copying lists

We have seen that Python variables are nothing but references to actual objects. The same holds true for lists. For this reason, manipulating lists gets a little tricky. By default, if we copy one list variable to another one by simply using the = operator, it won't actually create a duplicate or local copy of the list for that variable – instead, it would just create another reference and point the newly created reference toward the same memory location. Thus, when we make a change to the copied variable, the same change will be reflected in the original list. In the following example, we will create new isolated copies, where a change in the copied variable will not be reflected in the original list:

Now, let's look at how can we create a new copy of an existing list so that the changes to the new one do not cause any changes to the existing one:

Another way to create the isolated copy of the original list is to make use of the copy and deepcopy functions that are available in Python. A shallow copy constructs a new object and then inserts references to that object to the objects found in the original list. A deep copy, on the other hand, constructs a new compound object and then recursively inserts copies of the objects found in the original list: