Shallow copy vs deep copy | Rustam Zokirov

Deep copy is related to nested structures. If you have list of lists, then deepcopy() copies the nested lists also, so it is a recursive copy.
With shallow copy, you have a new outer list, but inner lists are references. So, a shallow copy doesn't create a copy of nested objects, instead it just copies the reference of nested objects.
Shallow copy:

copy.copy()
list()
Slicing [:]
list.copy()
Comprehension

import copy
spam = [[0, 1, 2, 3], 4, 5]
cheese = cоpy.copy(spam) # shallow copy

cheese.append(3)
cheese[0].append(3)

print(cheese) # [[0, 1, 2, 3, 3], 4, 5, 3]
print(spam) # [[0, 1, 2, 3, 3], 4, 5]

===============================================================
a = [[1,2,3]]
b = a[:] # shallow copy

print(id(a), id(b)) # different ids
b[0][0] = 999
print(a, b) # ANSWER: both will be modified

VS

a = [1,2,3]
b = a[:] # shallow copy

print(id(a), id(b))
b[0] = 999
print(a, b) # ANSWER: a will not be changed

===============================================================
import copy

old_list = [4, 5, 6, [2,3,3]]
new_list = copy.copy(old_list)

new_list[3] = [999]

print(old_list, new_list) # [4, 5, 6, [2, 3, 3]] [4, 5, 6, [999]]

===============================================================
l = [-9, -3, -12, -6, 15, 20]

def c(arr):
    arr[0] = "Rustam"
    
c(l[2:5])

l 
# [-9, -3, -12, -6, 15, 20]

Shallow copy examples

import copy
a = [[1, 2], [3, 4]]
b = a.copy()          # or a[:], or list(a) — all SHALLOW
b[0].append(99)
a                     # [[1, 2, 99], [3, 4]] — inner lists still shared

c = copy.deepcopy(a)  # recursively copies; handles cycles

list_ = [[[0]*3]*3]*3
list_[0][0][0] = 1

print(list_) # 9 ones
# [1 0 0][1 0 0][1 0 0]
# [1 0 0][1 0 0][1 0 0]
# [1 0 0][1 0 0][1 0 0]

def foo(x):
	x = [3, 2, 1]
	
def bar(x):
	x[0] = "hello"
	
arr = [1, 2, 3]
foo(arr)
print(arr) # 1, 2, 3

bar(arr)
print(arr) # hello, 2, 3