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Quiz: Tuples and Sets

Test your understanding of Python's tuple and set types, tuple unpacking, and set operations with these questions. Click "Show Answer" to reveal the correct answer and explanation.

1. What is the key difference between a tuple and a list?

  1. Tuples use parentheses; lists use square brackets, but otherwise they are identical
  2. Tuples are immutable (cannot be changed after creation); lists are mutable (can be changed)
  3. Tuples can only hold numbers; lists can hold any type
  4. Tuples are faster to create; lists are faster to access
Show Answer

The correct answer is B. The most important difference is mutability. Lists can have items added, removed, or changed. Tuples cannot — once created, their contents are fixed. Both support indexing, slicing, and iteration. Use a tuple when the data represents a fixed thing (like a coordinate) and a list when the collection needs to change.

Concept Tested: Tuple Type

2. How do you create a single-element tuple containing the number 42?

  1. (42)
  2. [42]
  3. {42}
  4. (42,)
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The correct answer is D. A trailing comma is required to tell Python you mean a tuple. (42) is just the integer 42 in parentheses — not a tuple. (42,) has the trailing comma that signals "this is a one-element tuple." For tuples with two or more items, no trailing comma is needed: (1, 2) is already clearly a tuple.

Concept Tested: Single-Element Tuple Syntax

3. What does tuple unpacking do?

  1. Removes all items from a tuple one at a time
  2. Converts a tuple into a list so its items can be changed
  3. Assigns each item in a tuple to a separate variable in one step
  4. Prints all items in a tuple on separate lines
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The correct answer is C. Tuple unpacking (also called destructuring) lets you write x, y = (10, 20) to assign 10 to x and 20 to y in a single line. The number of variables on the left must match the number of items in the tuple. This is the same mechanism that makes Python's one-line variable swap (a, b = b, a) work.

Concept Tested: Tuple Unpacking

4. What is a common use case for returning a tuple from a function?

  1. To make the function run faster
  2. To return multiple values from a function at once
  3. To prevent the caller from changing the return value
  4. To ensure the function can only be called once
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The correct answer is B. A function can only have one return statement, but you can pack multiple values into a tuple and return them all at once. For example, return min_val, max_val returns a tuple. The caller can then unpack it: lo, hi = find_range(data). This is cleaner than returning a list or using global variables.

Concept Tested: Tuples as Return Values

5. What happens when you add a duplicate item to a set?

  1. The set raises a ValueError
  2. The item is added a second time, creating a duplicate
  3. The duplicate is silently ignored — the set stays unchanged
  4. The original item is replaced by the new copy
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The correct answer is C. Sets automatically enforce uniqueness — no duplicates are allowed. If you add() an item that is already in the set, or create a set with repeated values like {1, 2, 2, 3}, Python silently ignores the duplicates. The set {1, 2, 2, 3} becomes {1, 2, 3}.

Concept Tested: Set Type

6. Given A = {1, 2, 3, 4} and B = {3, 4, 5, 6}, what is A & B?

  1. {1, 2, 3, 4, 5, 6} (all items from both)
  2. {1, 2} (items only in A)
  3. {3, 4} (items in both A and B)
  4. {5, 6} (items only in B)
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The correct answer is C. The & operator performs set intersection — it returns a new set containing only items that appear in both sets. Both 3 and 4 are in A and in B, so A & B = {3, 4}. The | operator is union (all items), and - is difference (in first but not second).

Concept Tested: Set Intersection

7. What does A | B produce for A = {1, 2, 3} and B = {3, 4, 5}?

  1. {3} (only the shared item)
  2. {1, 2, 4, 5} (items not in both)
  3. {1, 2} (items only in A)
  4. {1, 2, 3, 4, 5} (all unique items from both)
Show Answer

The correct answer is D. The | operator performs set union — it returns a new set containing all items from both sets, with no duplicates. {1, 2, 3} | {3, 4, 5} gives {1, 2, 3, 4, 5}. The shared item 3 appears only once in the result because sets do not allow duplicates.

Concept Tested: Set Union

8. What is the difference between s.remove(x) and s.discard(x) on a set?

  1. remove() removes by index; discard() removes by value
  2. remove() raises a KeyError if x is not found; discard() silently does nothing if x is not found
  3. remove() works on lists; discard() only works on sets
  4. They are identical — just two names for the same operation
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The correct answer is B. Both methods remove an item from a set by value, but they differ in error handling. remove(x) raises a KeyError if x is not in the set. discard(x) does nothing and raises no error if x is absent. Use discard() when you are not sure whether the item exists and do not want to check first.

Concept Tested: Set Methods

9. What is the quickest way to remove duplicates from a list in Python?

  1. Sort the list and remove adjacent duplicates with a loop
  2. Convert the list to a set with set(), which automatically removes duplicates
  3. Use list.remove_duplicates() (a built-in method)
  4. Iterate over the list and check each item with in before appending
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The correct answer is B. set(my_list) converts a list to a set, automatically discarding all duplicate values. If you need the result as a list again, wrap it: list(set(my_list)). The only caveat is that sets are unordered, so the original order is not preserved. There is no built-in remove_duplicates() method in Python.

Concept Tested: Set Type

10. What does A - B produce for A = {1, 2, 3, 4} and B = {3, 4, 5}?

  1. {5} (items only in B)
  2. {-2, -2, -2, -1} (subtracting each item)
  3. {1, 2} (items in A that are not in B)
  4. {1, 2, 5} (all unique items not shared)
Show Answer

The correct answer is C. The - operator performs set difference — it returns items that are in the first set but NOT in the second. {1, 2, 3, 4} - {3, 4, 5} gives {1, 2} because 3 and 4 are removed (they are in B) and 5 is not included (it was only in B). Note that A - B and B - A give different results.

Concept Tested: Set Difference