A **deep copy** refers to cloning an object. When we use the `=` operator, we are *not* cloning the object; instead, we reference our variable to the *same* object (a.k.a. shallow copy). 

This means that changing one variable's value affects the other variable's value because they are referring (or pointing) to the same object. This difference between a shallow and a deep copy is only applicable to objects that contain other objects, like lists and instances of a class.

<br>

# Method

To make a deep copy (or clone) of an object, we import the built-in `copy` module in Python. This module has the `deepcopy()` method which simplifies our task.

# Syntax

This function takes the object we want to clone as its only argument and *returns* the clone.

import copy

# Using '=' operator
x = [1, 2, 3]
y = x
x[0] = 5    # value of 'y' also changes as it is the SAME object
x[1] = 15
print "Shallow copy: ", y

# Using copy.deepcopy()
a = [10, 20, 30]
b = copy.deepcopy(a)
a[1] = 70   # value of 'b' does NOT change because it is ANOTHER object
print "Deep copy: ", b

How to make a deep copy in Python

Method

Syntax

Example