Queues (first-in, first-out) in Intro to Computing - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add an item to the end of the queue.

Intro to Computing

queue = []
queue.[1]('apple')

Drag options to blanks, or click blank then click option'

Apop

Bappend

Cremove

Dinsert

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'pop' removes an item instead of adding.

Using 'remove' deletes a specific item, not add.

Using 'insert' needs an index and is more complex.

To add an item to the end of a list (queue), we use append. This keeps the first-in, first-out order.

2fill in blank

medium

Complete the code to remove the first item from the queue.

Intro to Computing

queue = ['apple', 'banana', 'cherry']
first_item = queue.[1](0)

Drag options to blanks, or click blank then click option'

Apop

Bappend

Cremove

Dinsert

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'append' adds items instead of removing.

Using 'remove' needs the item value, not index.

Using 'insert' adds items, not removes.

To remove the first item from the queue, use pop(0). This removes and returns the item at index 0, following FIFO.

3fill in blank

hard

Fix the error in the code to correctly remove the first item from the queue.

Intro to Computing

queue = ['dog', 'cat', 'bird']
removed = queue.[1]

Drag options to blanks, or click blank then click option'

Adelete(0)

Bpop

Cremove(0)

Dpop(0)

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'pop()' removes the last item, not the first.

Using 'remove(0)' causes an error because remove expects a value.

Using 'delete(0)' is not a valid list method.

The pop method needs the index to remove the first item. pop(0) removes the first element. pop() without arguments removes the last item.

4fill in blank

hard

Fill both blanks to create a queue comprehension that keeps only items longer than 3 characters.

Intro to Computing

queue = ['cat', 'lion', 'dog', 'tiger']
filtered = [item for item in queue if len(item) [1] [2]]

Drag options to blanks, or click blank then click option'

A>

B3

C<

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' keeps shorter items, not longer.

Using '==' keeps only items exactly length 3.

Swapping the number and operator causes wrong filtering.

The comprehension keeps items where the length is greater than 3, so use len(item) > 3.

5fill in blank

hard

Fill all three blanks to create a dictionary showing each item and its position in the queue.

Intro to Computing

queue = ['red', 'blue', 'green']
positions = [1]: [2] for [3], color in enumerate(queue)}

Drag options to blanks, or click blank then click option'

A{color

Bindex

Dcolor

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping key and value reverses the dictionary.

Using wrong variable names causes errors.

Missing braces or colons breaks syntax.

The dictionary comprehension uses {color: index for index, color in enumerate(queue)} to map each color to its position.