# 1 a = [1, 2, 3] b = a b.append(4) # print(a) # print(a is b) # 2 a = 10 b = a # print(a is b) b += 5 # print(a) # print(b) #3 # data = { # ([1, 2, 3]): "a", # (1, 2, 3): "b" # } # print(data) #4 a = (1, [2, 3]) # a[1].append(4) # print(a) #5 a = [1, 2, 2, 3] b = set(a) # print(len(a), len(b))

Let's analyze each block of code and its behavior:

 a = [1, 2, 3]
 b = a
 b.append(4)
 print(a)       # [1, 2, 3, 4]
 print(a is b)  # True

Lists are mutable objects. Variables a and b refer to the same object. Changes through b are reflected in a. The is operator shows that they are the same object.

---

 a = 10
 b = a
 print(a is b)  # True (for small integers in Python)
 b += 5
 print(a)       # 10
 print(b)       # 15

Integers are immutable objects. When doing b += 5, a new object is created, and b now refers to 15, while a remains 10. is may be True for small numbers due to interning.

---

 data = {
     ([1, 2, 3]): "a",
     (1, 2, 3): "b"
 }
 print(data)

Dictionary keys must be hashable. The list [1,2,3] is mutable and unhashable, so this will raise a TypeError: unhashable type: 'list'. The tuple (1,2,3) is hashable and valid.

---

 a = (1, [2, 3])
 a[1].append(4)
 print(a)  # (1, [2, 3, 4])

A tuple is immutable, but if it contains mutable objects (like a list), their contents can be changed. Here, the list inside the tuple is modified.

---

 a = [1, 2, 2, 3]
 b = set(a)
 print(len(a), len(b))  # 4 3

A set contains only unique elements. The list has 4 elements, while the set has 3 unique elements.

---

In summary: it's important to understand the differences between mutable and immutable objects, reference and value semantics, and the requirements for dictionary keys.