The list.copy() method in Python is used to create a shallow copy of a list. A shallow copy means that it creates a new list containing references to the original list's elements. This method allows you to create a duplicate of the list that can be modified independently of the original list.

Syntax

new_list = original_list.copy()

Return Value

• The method returns a new list that is a shallow copy of the original list.

Example Usage

1. Creating a Copy of a List:

   original_list = [1, 2, 3, 4]
   copied_list = original_list.copy()  # Creates a copy of the original list
   print(copied_list)  # Output: [1, 2, 3, 4]
   

2. Modifying the Copied List: Changes made to the copied list do not affect the original list:

   original_list = [1, 2, 3]
   copied_list = original_list.copy()
   copied_list.append(4)  # Modifying the copied list
   print(original_list)    # Output: [1, 2, 3] (original list remains unchanged)
   print(copied_list)      # Output: [1, 2, 3, 4] (copied list is modified)
   

3. Shallow Copy Behavior: If the list contains mutable elements (like other lists), the copied list will still reference those mutable elements:

   original_list = [[1, 2], [3, 4]]
   copied_list = original_list.copy()
   copied_list[0][0] = 99  # Modifying a mutable element in the copied list
   print(original_list)    # Output: [[99, 2], [3, 4]] (original list is affected)
   print(copied_list)      # Output: [[99, 2], [3, 4]]
   

4. Copying an Empty List: Copying an empty list also works without errors:

   empty_list = []
   copied_empty = empty_list.copy()
   print(copied_empty)  # Output: []
   

5. Using the list() Constructor: You can also create a copy using the list() constructor, which gives the same result:

   original_list = [1, 2, 3]
   copied_list = list(original_list)  # Creates a copy using list()
   print(copied_list)  # Output: [1, 2, 3]
   

Summary

• list.copy() creates a shallow copy of a list, allowing for independent modifications.
• It does not affect the original list when changes are made to the copied list.
• If the original list contains mutable elements, changes to those elements will be reflected in both lists since they are still referencing the same objects.
• This method is a straightforward way to duplicate lists in Python without using slicing or the list() constructor.