Learn Python Copy Lists | Python Course

Copying lists in Python is an important concept because lists are mutable. If you copy a list incorrectly, changes in one list may unexpectedly affect another.

This topic explains all correct and incorrect ways to copy lists, with clear examples.

Why Copying Lists Matters

Lists store references, not values. So assigning one list to another does not create a new list.

Both variables point to the same list.

Copy a List Using `copy()`

The copy() method creates a shallow copy of the list.

Copy a List Using `list()` Constructor

Copy a List Using Slicing

Shallow Copy vs Deep Copy

Shallow Copy (Important Concept)

A shallow copy copies the outer list only.

Both lists are affected.

Deep Copy Using `copy` Module

A deep copy copies all nested objects.

Copy Using Loop

Copy Using List Comprehension

Compare Copied Lists

Common Mistakes

Using Assignment Instead of Copy

This does not create a copy.

Forgetting Deep Copy for Nested Lists

This is still a shallow copy.

When to Use Which Method

Method	Use Case
`copy()`	Simple, clean shallow copy
`list()`	Shallow copy from iterable
Slicing (`[:]`)	Quick shallow copy
`deepcopy()`	Nested lists
Loop / comprehension	Custom logic