Python - variable referencing and copy example

variable_reference_sample.py

import copy

# Base list
list1 = ["apple", "banana", "cherry"]

print("By default Python creates variables by reference")
list2 = list1

print("Now while list2 and list1 seems like two variables they refer to the same memory reference")
print("So modifying one variable will modify the others")
print("To confirm this we will print the memory address for both the variables")
print("Memory address of list1: " + str(id(list1))) 
print("Memory address of list2: " + str(id(list2)))

print("Now let\'s modify list1 and we will confirm that list2 is also affected and vice versa")
print("Adding an item to list1")
list1.append("orange")
print(list1)
print(list2)

print("Removing an item from list2")
list2.remove("orange")
print(list1)
print(list2)

print("Now let us try shallow copy where distinct memory addresses are created for each variable. For this we will use copy module.")
list2 = copy.copy(list1)

print("We will confirm this by printing the memory address of list1 and list2")
print("Memory address of list1: " + str(id(list1))) 
print("Memory address of list2: " + str(id(list2)))

print("Now we will add an item to list1 and list2 will remain intact")
list1.append("orange")
print(list1)
print(list2)

print("Now we will remove an item from list2 and list1 will remain intact")
list2.remove("cherry")
print(list1)
print(list2)