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PYTHON LIST DEEP COPY

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PYTHON LIST DEEP COPY

INTRODUCTION

In deep copy operation, changes in original list does not have the impact on copied list and vice-versa.

There are three ways we can create deep copy in Python.

  • List Slicing Operation
  • Importing copy Module to use deepcopy() method
  • copy() Method for Primitive Data Types

List Slicing Operation

# Deep Copy operation using Slicing operator[:] example 1


org_list = [400, 200, 600, 100, 150, 500] 
print("\nElement of original list ->", org_list)

copy_list = org_list[:]
print("\nElement of copied list ->", copy_list)

# Removing the last element from the copied list 
copy_list.remove(600)

print("\nElement of original list ->", org_list)
print("\nElement of copied list ->", copy_list)

# UPdating the first element of the original list 
org_list[0] = 700

print("\nElement of original list ->", org_list)
print("\nElement of copied list ->", copy_list)

PYTHON LIST DEEP COPY : Output

Element of original list -> [400, 200, 600, 100, 150, 500]

Element of copied list -> [400, 200, 600, 100, 150, 500]

Element of original list -> [400, 200, 600, 100, 150, 500]

Element of copied list -> [400, 200, 100, 150, 500]

Element of original list -> [700, 200, 600, 100, 150, 500]

Element of copied list -> [400, 200, 100, 150, 500]

In the above example, we can see that we have removed the element 600 from copied list and update the 1st element of original list to 700. But the impact of change in one list didn’t affect the other list. So, this is the deep copy.

We will now check the string list as well.

# Deep Copy operation using Slicing operator[:] example 2


org_list = ['Python', 'Java', 'C++', 'C', 'PHP', 'XML'] 
print("\nElement of original list ->", org_list)

copy_list = org_list[:]
print("\nElement of copied list ->", copy_list)

# Removing the last element from the copied list 
copy_list.remove('C++')

print("\nElement of original list ->", org_list)
print("\nElement of copied list ->", copy_list)

# UPdating the first element of the original list 
org_list[1] = 'Word'

print("\nElement of original list ->", org_list)
print("\nElement of copied list ->", copy_list)

PYTHON LIST DEEP COPY : Output

Element of original list -> ['Python', 'Java', 'C++', 'C', 'PHP', 'XML']

Element of copied list -> ['Python', 'Java', 'C++', 'C', 'PHP', 'XML']

Element of original list -> ['Python', 'Java', 'C++', 'C', 'PHP', 'XML']

Element of copied list -> ['Python', 'Java', 'C', 'PHP', 'XML']

Element of original list -> ['Python', 'Word', 'C++', 'C', 'PHP', 'XML']

Element of copied list -> ['Python', 'Java', 'C', 'PHP', 'XML']

Now we can see the same impact in string list as well.

Importing copy Module to use deepcopy() method

Impact on Primitive Data Type

import copy

org_list = [400, 200, 600, 100, 150, 500] 
print("\nElement of original list ->", org_list)

copy_list = copy.deepcopy(org_list)
print("\nElement of copied list ->", copy_list)

# Removing the last element from the copied list 
copy_list.remove(600)

print("\nElement of original list ->", org_list)
print("\nElement of copied list ->", copy_list)

# UPdating the first element of the original list 
org_list[0] = 700

print("\nElement of original list ->", org_list)
print("\nElement of copied list ->", copy_list)

PYTHON LIST DEEP COPY : Output

Element of original list -> [400, 200, 600, 100, 150, 500]

Element of copied list -> [400, 200, 600, 100, 150, 500]

Element of original list -> [400, 200, 600, 100, 150, 500]

Element of copied list -> [400, 200, 100, 150, 500]

Element of original list -> [700, 200, 600, 100, 150, 500]

Element of copied list -> [400, 200, 100, 150, 500]

In the above example, we have imported the copy module in our program. After using deepcopy() method we can check that both original list and copied list have different set of elements. So the impact of changes in one list is not visible in the other list.

# Deep Copy operation using deepcopy() method example 2

import copy

org_list = ['Python', 'Java', 'C++', 'C', 'PHP', 'XML'] 
print("\nElement of original list ->", org_list)

copy_list = copy.deepcopy(org_list)
print("\nElement of copied list ->", copy_list)

# Removing the last element from the copied list 
copy_list.remove('C++')

print("\nElement of original list ->", org_list)
print("\nElement of copied list ->", copy_list)

# UPdating the first element of the original list 
org_list[1] = 'Word'

print("\nElement of original list ->", org_list)
print("\nElement of copied list ->", copy_list)

PYTHON LIST DEEP COPY : Output

Element of original list -> ['Python', 'Java', 'C++', 'C', 'PHP', 'XML']

Element of copied list -> ['Python', 'Java', 'C++', 'C', 'PHP', 'XML']

Element of original list -> ['Python', 'Java', 'C++', 'C', 'PHP', 'XML']

Element of copied list -> ['Python', 'Java', 'C', 'PHP', 'XML']

Element of original list -> ['Python', 'Word', 'C++', 'C', 'PHP', 'XML']

Element of copied list -> ['Python', 'Java', 'C', 'PHP', 'XML']

For string list also the deepcopy() method has the same impact.

Impact on Complex Data Type

Now we will see the impact of deepcopy() on list with complex data type.

# Deep Copy operation using deepcopy() method example 3

import copy

int_list = [1, 2, 5]
str_list = ['Python', 'Java', 'C++']

org_list = [400, 200, 600, 100, 150, 500, int_list, str_list] 
print("\nElement of original list ->", org_list)

copy_list = copy.deepcopy(org_list)
print("\nElement of copied list ->", copy_list)

# Removing the last element from the copied list 
int_list.remove(5)

print("\nElement of original list ->", org_list)
print("\nElement of copied list ->", copy_list)

# UPdating the first element of the original list 
str_list[2] = 'Word'

print("\nElement of original list ->", org_list)
print("\nElement of copied list ->", copy_list)

PYTHON LIST DEEP COPY : Output

Element of original list -> [400, 200, 600, 100, 150, 500, [1, 2, 5], ['Python', 'Java', 'C++']]

Element of copied list -> [400, 200, 600, 100, 150, 500, [1, 2, 5], ['Python', 'Java', 'C++']]

Element of original list -> [400, 200, 600, 100, 150, 500, [1, 2], ['Python', 'Java', 'C++']]

Element of copied list -> [400, 200, 600, 100, 150, 500, [1, 2, 5], ['Python', 'Java', 'C++']]

Element of original list -> [400, 200, 600, 100, 150, 500, [1, 2], ['Python', 'Java', 'Word']]

Element of copied list -> [400, 200, 600, 100, 150, 500, [1, 2, 5], ['Python', 'Java', 'C++']]

In the above example, we have used two smaller list int_list and str_list inside the original list. We have modified both the smaller list. But the impact is visible only in the original list. So the deep copy impact is still intact for list having complex data type as well.

copy() Method for Primitive Data Types

If we use list having primitive data type only, then copy() method will also work like deep copy.

Integer Data Type

# Deep Copy operation using copy() method for primitive data types example 1

import copy

org_list = [400, 200, 600, 100, 150, 500] 
print("\nElement of original list ->", org_list)

copy_list = copy.deepcopy(org_list)
print("\nElement of copied list ->", copy_list)

# Removing the last element from the copied list 
org_list.remove(600)

print("\nElement of original list ->", org_list)
print("\nElement of copied list ->", copy_list)

# UPdating the first element of the original list 
copy_list[0] = 700

print("\nElement of original list ->", org_list)
print("\nElement of copied list ->", copy_list)

PYTHON LIST DEEP COPY : Output

Element of original list -> [400, 200, 600, 100, 150, 500]

Element of copied list -> [400, 200, 600, 100, 150, 500]

Element of original list -> [400, 200, 100, 150, 500]

Element of copied list -> [400, 200, 600, 100, 150, 500]

Element of original list -> [400, 200, 100, 150, 500]

Element of copied list -> [700, 200, 600, 100, 150, 500]

String Data Type

# Deep Copy operation using copy() method for primitive data types example 2

import copy

org_list = ['Python', 'Java', 'C++', 'C', 'PHP', 'XML'] 
print("\nElement of original list ->", org_list)

copy_list = copy.deepcopy(org_list)
print("\nElement of copied list ->", copy_list)

# Removing the last element from the copied list 
org_list.remove('C++')

print("\nElement of original list ->", org_list)
print("\nElement of copied list ->", copy_list)

# UPdating the first element of the original list 
copy_list[2] = 'Word'

print("\nElement of original list ->", org_list)
print("\nElement of copied list ->", copy_list)

PYTHON LIST DEEP COPY : Output

Element of original list -> ['Python', 'Java', 'C++', 'C', 'PHP', 'XML']

Element of copied list -> ['Python', 'Java', 'C++', 'C', 'PHP', 'XML']

Element of original list -> ['Python', 'Java', 'C', 'PHP', 'XML']

Element of copied list -> ['Python', 'Java', 'C++', 'C', 'PHP', 'XML']

Element of original list -> ['Python', 'Java', 'C', 'PHP', 'XML']

Element of copied list -> ['Python', 'Java', 'Word', 'C', 'PHP', 'XML']

Both the example mentioned above, the original list and copied list are not in sync. So by using the copy() method we can achieve the deep copy feature if the elements in the list are of primitive data type.

PYTHON LIST DEEP COPY : Output
PYTHON LIST DEEP COPY : Output

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