Chapter 7

Question 1

What is a sequence in Python?

Answer 1

An object that contains multiple items of data stored one after another (e.g., lists, tuples)

Question 2

What is the difference between a list and a tuple?

Answer 2

Lists are mutable; tuples are immutable

Question 3

What is a list?

Answer 3

An object containing multiple data items, called elements, defined with brackets: [item1, item2, …]

Question 4

What is a repetition operator for lists?

Answer 4

• operator, which repeats a list n times: list * n

Question 5

How do you iterate over a list?

Answer 5

With a for loop: for x in list:

Question 6

What is an index in a list?

Answer 6

A number specifying the position of an element; first element is at index 0

Question 7

What do negative indexes in lists represent?

Answer 7

Positions relative to the end of the list; -1 is the last element

Question 8

What does the len() function return for a list?

Answer 8

The number of elements in the list

Question 9

What happens if you use an invalid index?

Answer 9

An IndexError exception is raised

Question 10

Are lists mutable?

Answer 10

Yes, list elements can be changed with assignment

Question 11

How do you concatenate two lists?

Answer 11

Using + or +=

Question 12

What is list slicing?

Answer 12

Extracting a span of items: list[start:end], up to but not including end

Question 13

What does the in operator do with lists?

Answer 13

Tests whether an item is in a list; returns True or False

Question 14

What does the not in operator do with lists?

Answer 14

Tests whether an item is not in a list

Question 15

What does append(item) do?

Answer 15

Adds an item to the end of a list

Question 16

What does count(item) do?

Answer 16

Returns the number of times an item appears in a list

Question 17

What does index(item) do?

Answer 17

Returns the index of the first occurrence of an item; raises ValueError if not found

Question 18

What does insert(index, item) do?

Answer 18

Inserts an item at a specific index

Question 19

What does sort() do for lists?

Answer 19

Sorts elements in ascending order

Question 20

What does remove(item) do?

Answer 20

Removes the first occurrence of an item

Question 21

What does reverse() do for lists?

Answer 21

Reverses the order of list elements

Question 22

What does the del statement do for lists?

Answer 22

Removes an element at a specified index: del list[i]

Question 23

What do sum(), min(), and max() do for lists?

Answer 23

Return the total, the lowest value, and the highest value in a numeric list

Question 24

How do you properly copy a list?

Answer 24

Create a new list and copy elements using a loop or concatenation

Question 25

How do you calculate the average of numbers in a list?

Answer 25

Find the sum of values and divide by len(list)

Question 26

What does writelines() do?

Answer 26

Saves the contents of a list to a file (does not add \n automatically)

Question 27

What does readlines() do?

Answer 27

Reads data from a file into a list

Question 28

What is a list comprehension?

Answer 28

A concise expression that creates a new list by iterating over an existing one

Question 29

Example of list comprehension?

Answer 29

[item**2 for item in list1] creates a list of squared values

Question 30

How do you add conditions to a list comprehension?

Answer 30

Include an if clause: [item for item in list1 if item < 10]

Question 31

What is a two-dimensional list?

Answer 31

A list containing other lists, often thought of in rows and columns

Question 32

How do you access elements in a two-dimensional list?

Answer 32

With two indexes, e.g., list[row][col]

Question 33

What is a tuple?

Answer 33

An immutable sequence; once created, it cannot be changed

Question 34

How do you create a tuple?

Answer 34

(item1, item2, …) or (item1,) for a single element

Question 35

What operations do tuples support?

Answer 35

Indexing, slicing, len, min, max, in, +, *, and some methods like index()

Question 36

What methods are not supported by tuples?

Answer 36

append, remove, insert, reverse, and sort

Question 37

Can a tuple hold mutable objects?

Answer 37

Yes, and the mutable object’s contents can still change

Question 38

Why use tuples?

Answer 38

Faster than lists, provide safety, and required in some operations

Question 39

How do you convert between lists and tuples?

Answer 39

Use list() and tuple() functions