Shallow copy vs Deep copy

import copy
 
original = [[1, 2], [3, 4]]
shallow = original.copy()  # or copy.copy(original)
 
# Sửa inner list
shallow[0].append(5)
 
print(original)  # [[1, 2, 5], [3, 4]] ❌
print(shallow)   # [[1, 2, 5], [3, 4]]

import copy
 
original = [[1, 2], [3, 4]]
deep = copy.deepcopy(original)
 
# Sửa inner list
deep[0].append(5)
 
print(original)  # [[1, 2], [3, 4]] ✅
print(deep)      # [[1, 2, 5], [3, 4]]

# List phẳng
nums = [1, 2, 3]
copy_nums = nums.copy()  # ✅ Shallow đủ
 
# Dict phẳng
data = {"name": "Alice", "age": 25}
copy_data = data.copy()  # ✅ Shallow đủ

# Nested list
matrix = [[1, 2], [3, 4]]
copy_matrix = copy.deepcopy(matrix)  # ✅ Cần deep
 
# Dict với list values
data = {"users": [{"name": "Alice"}]}
copy_data = copy.deepcopy(data)  # ✅ Cần deep

import copy
import timeit
 
data = [[1, 2, 3] * 100 for _ in range(100)]
 
# Shallow - Nhanh
timeit.timeit(lambda: data.copy(), number=10000)
 
# Deep - Chậm hơn
timeit.timeit(lambda: copy.deepcopy(data), number=10000)

# Shallow
new = original.copy()
 
# Deep
import copy
new = copy.deepcopy(original)