LRANGE for reading elements in Redis - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to get the first 3 elements from the list 'mylist'.

Redis

LRANGE mylist 0 [1]

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

A2

B3

C-1

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using 3 as the end index returns 4 elements.

Using -1 returns the entire list.

The LRANGE command uses zero-based indexes. To get the first 3 elements, the end index should be 2.

2fill in blank

medium

Complete the code to get the last 4 elements from the list 'tasks'.

Redis

LRANGE tasks [1] -1

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

A4

B-4

C-3

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using 4 as start index skips first 4 elements instead of last 4.

Using -3 returns only last 3 elements.

Using a negative start index counts from the end. -4 means start from the 4th last element.

3fill in blank

hard

Fix the error in the code to get elements from index 2 to 5 in 'myqueue'.

Redis

LRANGE myqueue 2 [1]

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

A6

B-1

C5

D4

Attempts:

3 left

💡 Hint

Common Mistakes

Using 6 returns one extra element.

Using 4 returns one less element.

The end index is inclusive, so to get elements from 2 to 5, use 5 as the end index.

4fill in blank

hard

Fill both blanks to get elements from the 3rd to the 7th position in 'events'.

Redis

LRANGE events [1] [2]

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

A2

B3

C6

D7

Attempts:

3 left

💡 Hint

Common Mistakes

Using 3 (B) as start index gets from 4th position.

Using 7 (D) as end index gets up to 8th position.

Indexes start at 0, so the 3rd position (1-based) is index 2 (A), 7th position is index 6 (C). End index is inclusive.

5fill in blank

hard

Fill all three blanks to get elements from index 1 to 4 from 'queue' and store in variable 'result'.

Redis

result = redis.call('LRANGE', 'queue', [1], [2]) -- expecting [3] elements

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

A1

B4

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Expecting 3 elements instead of 4.

Using wrong start or end indexes.

Start=1 (A), end=4 (B) inclusive returns 4 elements (C) at indices 1,2,3,4. Number = end - start + 1 = 4.