Python List copy()

 # mixed list prime_numbers = [2, 3, 5] 
# copying a list numbers = prime_numbers.copy()
 print('Copied List:', numbers) # Output: Copied List: [2, 3, 5]

copy() Syntax

The syntax of the copy() method is:

 new_list = list.copy()

copy() Parameters

The copy() method doesn't take any parameters.

copy() Return Value

The copy() method returns a new list. It doesn't modify the original list.

Example: Copying a List

 # mixed list my_list = ['cat', 0, 6.7] 
# copying a list new_list = my_list.copy()
 print('Copied List:', new_list)

Output

 Copied List: ['cat', 0, 6.7]

If you modify the new_list in the above example, my_list will not be modified.

List copy using =

We can also use the = operator to copy a list. For example,

 old_list = [1, 2, 3] new_list = old_list

Howerver, there is one problem with copying lists in this way. If you modify new_list, old_list is also modified. It is because the new list is referencing or pointing to the same old_list object.

 old_list = [1, 2, 3] 
# copy list using = new_list = old_list
 # add an element to list new_list.append('a') print('New List:', new_list) print('Old List:', old_list)

Output

 Old List: [1, 2, 3, 'a'] New List: [1, 2, 3, 'a']

However, if you need the original list unchanged when the new list is modified, you can use the copy() method.

Related tutorial: Python Shallow Copy Vs Deep Copy

Example: Copy List Using Slicing Syntax

 # shallow copy using the slicing syntax # mixed list list = ['cat', 0, 6.7] 
# copying a list using slicing new_list = list[:]
 # Adding an element to the new list new_list.append('dog') # Printing new and old list print('Old List:', list) print('New List:', new_list)

Output

 Old List: ['cat', 0, 6.7] New List: ['cat', 0, 6.7, 'dog']

Also Read:

• NumPy copy()