shallow_deep.py

a_string = ['10', 'days', 'to', 'departure']
b_string = a_string

print('a_string identity:', id(a_string))
print('b_string identity:', id(b_string))
print('The result of the value comparison:', a_string == b_string)
print('The result of the identity comparison:', a_string is b_string)

print()

a_string = ['10', 'days', 'to', 'departure']
b_string = ['10', 'days', 'to', 'departure']

print('a_string identity:', id(a_string))
print('b_string identity:', id(b_string))
print('The result of the value comparison:', a_string == b_string)
print('The result of the identity comparison:', a_string is b_string)



#-------------------------------------#
#shallow copy and deep copy

import copy
print("Part 1")
print("Let's make a copy")
a_list = [10, "banana", [997, 123]]
b_list = a_list[:]
print("a_list contents:", a_list)
print("b_list contents:", b_list)
print("Is it the same object?", a_list is b_list)

print()
print("Part 2")
print("Let's modify b_list[2]")
b_list[2][0] = 112
print("a_list contents:", a_list)
print("b_list contents:", b_list)
print("Is it the same object?", a_list is b_list)


print("Let's make a deep copy")
a_list = [10, "banana", [997, 123]]
b_list = copy.copy(a_list)
print("a_list contents:", a_list)
print("b_list contents:", b_list)
print("Is it the same object?", a_list is b_list)

print()
print("Let's modify b_list[2]")
b_list[2][0] = 112
print("a_list contents:", a_list)
print("b_list contents:", b_list)
print("Is it the same object?", a_list is b_list)


#=========================================#

import copy
import time

a_list = [(1,2,3) for x in range(1_000_000)]

print('Single reference copy')
time_start = time.time()
b_list = a_list
print('Execution time:', round(time.time() - time_start, 3))
print('Memory chunks:', id(a_list), id(b_list))
print('Same memory chunk?', a_list is b_list)

print()

print('Shallow copy')
time_start = time.time()
b_list = a_list[:]
print('Execution time:', round(time.time() - time_start, 3))
print('Memory chunks:', id(a_list), id(b_list))
print('Same memory chunk?', a_list is b_list)

print()

print('Deep copy')
time_start = time.time()
b_list = copy.deepcopy(a_list)
print('Execution time:', round(time.time() - time_start, 3))
print('Memory chunks:', id(a_list), id(b_list))
print('Same memory chunk?', a_list is b_list)