LRANGE for reading elements in Redis - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the LRANGE command do in Redis?

LRANGE returns a specified range of elements from a list stored at a given key. It reads elements between the start and stop indexes.

beginner

How do you specify the range of elements to read with LRANGE?

You provide two numbers: the start index and the stop index. Both are zero-based and inclusive.

intermediate

What happens if the stop index in LRANGE is larger than the list length?

LRANGE will return elements up to the end of the list without error.

intermediate

How does LRANGE handle negative indexes?

Negative indexes count from the end of the list. For example, -1 is the last element, -2 is the second last, and so on.

beginner

Example: What does LRANGE mylist 0 2 return if mylist = ["a", "b", "c", "d"]?

It returns ["a", "b", "c"] — the first three elements from index 0 to 2 inclusive.

What does LRANGE mylist 1 3 return if mylist = ["x", "y", "z", "w"]?

A ["z", "w"]

B ["x", "y", "z"]

C ["y", "z", "w"]

D ["y", "z"]

Indexes 1 to 3 include elements at positions 1, 2, and 3: "y", "z", and "w".

If you want to get the last element of a list using LRANGE, which indexes do you use?

A -1 -1

B 0 0

C 0 -1

D -2 -1

Using -1 for both start and stop returns only the last element.

What will LRANGE return if the start index is greater than the stop index?

A An error

B An empty list

C The whole list

D The first element only

LRANGE returns an empty list if start > stop.

How does LRANGE treat the stop index?

A Ignored

B Exclusive (stop element not included)

C Always zero

D Inclusive (stop element included)

The stop index is inclusive, so the element at that index is included in the result.

If a list has 5 elements, what does LRANGE mylist 0 10 return?

A The first 5 elements

B An empty list

C An error because 10 is out of range

D Only the first element

LRANGE returns all elements up to the end if stop index is beyond list length.

Explain how to use LRANGE to read elements from a Redis list, including how indexes work.

Think about how you pick a slice of a list using start and stop positions.

Describe what happens when LRANGE is used with indexes outside the list's length or with negative indexes.

Consider how LRANGE handles boundaries and negative numbers.