Question 1 of Quiz 03

Which data structures are sequences?

list (Only list is an ordered sequence. set and dict are unordered collections.)

Which data structures are mutable?

list, set, dict (All three can be modified after creation.)

Which can contain duplicate values?

list, dict (list: duplicates allowed. dict: values can duplicate, but keys must be unique. set enforces uniqueness.)

Which uses key-value pairs?

dict (Example: {"name": "Alice"}. list and set store individual elements.)

Which does NOT guarantee element order?

set (Even in modern Python, set is unordered. list and dict preserve insertion order.)

Which allows indexing with [ ]?

list, dict (list: by position (e.g., lst[0]). dict: by key (e.g., d["key"]). set is unindexed.)

Most efficient for checking if an item exists?

set, dict (O(1) lookup time. list is O(n) since it checks each item sequentially.)

Best for ordered elements + duplicates?

list (Example: ["a", "b", "a"] keeps order and allows repeats.)

Which uses .add() to insert elements?

set (Example: s.add(3). list uses .append()/.insert(), dict uses [key] = value.)

Best for iterating + modifying a sequence?

list (Optimized for sequential access and in-place changes.)

Best for PID → email lookups?

dict (Example: {"12345": ""}. Fast key-based retrieval.)

Literal syntax uses { }?

set, dict (set: {1, 2, 3}. dict: {"a": 1}. list uses [ ].)

Literal syntax uses [ ]?

list (Example: [1, 2, 3]. set/dict use { }.)

Can be iterated with for..in?

list, set, dict (All are iterable. dict iterates over keys by default.)

Works with len()?

list, set, dict (All return the number of items. dict counts key-value pairs.)

Best for set operations (union/intersection)?

set (Methods like s1.union(s2) are native to set.)

Best for ordered messages in a chat app?

list (Keeps insertion order: ["msg1", "msg2"].)

Best for counting word frequencies?

dict (Example: {"word": 5}. Efficient increments with counts[word] += 1.)

Allows custom index types (e.g., strings)?

dict (Keys can be str, int, tuple, etc. list only uses integer indices.)