How to Check If a List is Empty in R

What do we mean when we say an empty list? An empty list does not contain elements. It exists in the memory but does not have any elements stored in it.

The efficient way to check if a list is empty in R is by comparing its length with 0. If it returns TRUE, that means the list is empty; otherwise not.

You can check the length of any input object using the length() function.

Syntax

length(main_list) == 0

Example

You can create an empty list by using the list() function, which does not accept any arguments.

main_list <- list()

print(length(main_list) == 0) # TRUE

As expected, it returns TRUE since the input list is empty.

Let’s take another scenario where the list is not empty.

main_list <- list(c(19, 21), c("KB", "KL"))

print(length(main_list) == 0) # FALSE

As expected, it returns FALSE since the input list object is not empty anymore.

Shorter way to check

You can use the shorter syntax “!length()”.

main_list <- list()

print(!length(main_list)) # TRUE

And for non-empty lists:

main_list <- list(c(19, 21), c("KB", "KL"))

print(!length(main_list)) # FALSE

That’s all!