When working with lists in Python, understanding how copying works is essential—especially if your list contains nested structures. Below are the key concepts, explained in a simple and practical way.
1. Shallow Copy vs. Deep Copy
Copying a list isn’t always as straightforward as it seems. Python gives you two different approaches depending on how independent you want the copied list to be.
Shallow Copy (Using copy() Method)
A shallow copy creates a new outer list, but inner elements are still shared by reference.
This means:
- Changing a nested item affects both lists.
- Only the top-level structure is duplicated.
Deep Copy (Using copy.deepcopy() Function)
A deep copy goes further by recursively duplicating all nested objects.
This ensures that every level of the copied list behaves independently.
Example:
import copy
deep_list = copy.deepcopy(nested)
#Output
Deep copying is especially useful when you’re working with multi-dimensional data, nested dictionaries, or complex list structures.