Python — Data structures (list, tuple, dict, set)

Questions in this quiz

1. 1. What is l after this?

   l = [1, 2, 3]
   l.append([4, 5])
   print(l)

   1. [1, 2, 3, 4, 5]
   2. [1, 2, 3, [4, 5]]
   3. [[1, 2, 3], [4, 5]]
   4. Error
2. 2. Which built-in is immutable?
   1. list
   2. dict
   3. set
   4. tuple
3. 3. Average complexity of x in d for a dict?
   1. O(1)
   2. O(log n)
   3. O(n)
   4. O(n log n)
4. 4. What is printed?

   d = {'a': 1, 'b': 2}
   d.setdefault('a', 99)
   d.setdefault('c', 3)
   print(d)

   1. {'a': 1, 'b': 2, 'c': 3}
   2. {'a': 99, 'b': 2, 'c': 3}
   3. {'a': 1, 'b': 2}
   4. KeyError
5. 5. How do you de-duplicate while preserving order?
   1. set(lst)
   2. list(dict.fromkeys(lst))
   3. sorted(set(lst))
   4. tuple(lst)
6. 6. What is printed?

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

   1. [1, 2, 3]
   2. [1, 2, 3, 4]
   3. [4, 1, 2, 3]
   4. Error
7. 7. Which creates the set {1, 2, 3}?
   1. {}
   2. set()
   3. {1, 2, 3}
   4. [1, 2, 3]
8. 8. Given t = (10, 20, 30, 40), what is t[1:3]?
   1. (10, 20)
   2. (20, 30)
   3. (20, 30, 40)
   4. [20, 30]
9. 9. Which op is not allowed on a set?
   1. s.add(1)
   2. s | {2}
   3. s[0]
   4. s.discard(1)
10. 10. What does this print?

    nums = [3, 1, 4, 1, 5, 9, 2]
    print(sorted(nums, reverse=True)[:3])

    1. [1, 2, 3]
    2. [9, 5, 4]
    3. [3, 1, 4]
    4. [9, 5, 4, 3]
11. 11. What does this print?

    m = [[0]*3]*3
    m[0][0] = 9
    print(m)

    1. [[9, 0, 0], [0, 0, 0], [0, 0, 0]]
    2. [[9, 0, 0], [9, 0, 0], [9, 0, 0]]
    3. [[0, 0, 0], [0, 0, 0], [0, 0, 0]]
    4. Error
12. 12. Which removes the last element in amortized O(1)?
    1. lst.pop(0)
    2. lst.pop()
    3. del lst[len(lst)//2]
    4. lst.remove(lst[-1])
13. 13. Best structure for O(1) FIFO at both ends?
    1. list
    2. collections.deque
    3. set
    4. tuple
14. 14. What does this print?

    from collections import Counter
    c = Counter("mississippi")
    print(c.most_common(2))

    1. [('i', 4), ('s', 4)]
    2. [('s', 4), ('i', 4)]
    3. [('m', 1), ('p', 2)]
    4. Error
15. 15. What does frozenset({1,2}) in {frozenset({1,2}): 'x'} return?
    1. True
    2. False
    3. TypeError
    4. None
16. 16. What is the output?

    d = {'a': 1, 'b': 2}
    for k, v in sorted(d.items(), key=lambda kv: -kv[1]):
        print(k, v)

    1. a 1 then b 2
    2. b 2 then a 1
    3. a 2 then b 1
    4. Error
17. 17. What does this print?

    lst = [1, 2, 3, 4, 5]
    print(lst[::-2])

    1. [5, 3, 1]
    2. [1, 3, 5]
    3. [5, 4, 3]
    4. [4, 2]
18. 18. Which value is valid as a dict key?
    1. A list
    2. A set
    3. A tuple of hashable items
    4. A dict
19. 19. Difference between {} and set()?
    1. None
    2. {} is an empty dict; set() is an empty set
    3. {} is immutable
    4. set() uses less memory
20. 20. What is printed?

    d = {'x': 1, 'y': 2, 'z': 3}
    view = d.keys()
    del d['x']
    print(list(view))

    1. ['x', 'y', 'z']
    2. ['y', 'z']
    3. ['x']
    4. RuntimeError