How do I copy a list from one list to another in Python?

22 Answers

You can use the builtin list.copy() method (available since Python 3.3): new_list = old_list.copy()
You can slice it: new_list = old_list[:]
You can use the built in list() function: new_list = list(old_list)
You can use generic copy.copy() : import copy new_list = copy.copy(old_list)

What does Copy () do in Python?

The Python copy() method creates a copy of an existing list. The copy() method is added to the end of a list object and so it does not accept any parameters. copy() returns a new list. Python includes a built-in function to support creating a shallow copy of a list: copy().

Is list deep copy Python?

We can create shallow and deep copies in Python. A deep copy of a list is to create a new list and then recursively insert in it the copies of the original list’s elements. It refers to cloning a list, and any changes made in the original list do not affect the cloned list.

Does slicing create a new list?

In short, slicing is a flexible tool to build new lists out of an existing list. Python supports slice notation for any sequential data type like lists, strings, tuples, bytes, bytearrays, and ranges. Also, any new data structure can add its support as well.

How do you deep copy an array in Python?

A deep copy can be made using copy. deepcopy() function. This works by constructing a new object and then recursively inserting copies of the objects found in the original. Note that a deep copy may result in the recursive loop for recursive objects, i.e., compound objects that contain a reference to themselves.

What is a true copy of a list in Python?

True copy of a list means that the elements of the original list are copied to new memory locations and the new list contains references to these new memory locations for each element of the list. Hence, in case of true copy changes made to the original list will not reflect in the copied list and vice versa.

What is the difference between deep and shallow copy?

A shallow copy constructs a new compound object and then (to the extent possible) inserts references into it to the objects found in the original. A deep copy constructs a new compound object and then, recursively, inserts copies into it of the objects found in the original.

How do I copy a list using slicing?

First: Copying by Slicing When you omit the start index and the end index from the slice, then your slice will start from the beginning of the list all the way to the end of the list. And because slicing creates a new object, then the above code effectively copies or clones the whole list into another list.

Does slicing in Python create a new array?

Python supports the slicing of arrays. It is the creation of a new sub-array from the given array on the basis of the user-defined starting and ending indices.

How do you do a deep copy in Python?

A deep copy creates a new object and recursively adds the copies of nested objects present in the original elements. Let’s continue with example 2. However, we are going to create deep copy using deepcopy() function present in copy module….Table of Contents