Deep copy and shallow copy [interview question 3]

The difference between deep copy and shallow copy

Shallow copy , To reallocate a piece of memory , Create a new object , But the element inside is the reference of each sub object in the original object . because l2 The address of the previous object is used , So when [2,3,4] When adding data ,l2 The data of has also changed

import copy

def cal(l):
	l[-1].append(6)
	l.append(5)
	return l

l = [1,2,[2,3,4]]
l2 = l.copy()
print(cal(l))
print(l2)

# Output results 
#[1, 2, [2, 3, 4, 6], 5]
#[1, 2, [2, 3, 4, 6]]

Deep copy , To reallocate a piece of memory , Create a new object , And the elements in the original object , In a recursive way , Copy to the new object by creating a new sub object . therefore , The new object has nothing to do with the original object .