checkList: Check if an argument is a list
In checkmate: Fast and Versatile Argument Checks

checkList

R Documentation

Check if an argument is a list

Description

Check if an argument is a list

Usage

checkList(
  x,
  types = character(0L),
  any.missing = TRUE,
  all.missing = TRUE,
  len = NULL,
  min.len = NULL,
  max.len = NULL,
  unique = FALSE,
  names = NULL,
  null.ok = FALSE
)

check_list(
  x,
  types = character(0L),
  any.missing = TRUE,
  all.missing = TRUE,
  len = NULL,
  min.len = NULL,
  max.len = NULL,
  unique = FALSE,
  names = NULL,
  null.ok = FALSE
)

assertList(
  x,
  types = character(0L),
  any.missing = TRUE,
  all.missing = TRUE,
  len = NULL,
  min.len = NULL,
  max.len = NULL,
  unique = FALSE,
  names = NULL,
  null.ok = FALSE,
  .var.name = vname(x),
  add = NULL
)

assert_list(
  x,
  types = character(0L),
  any.missing = TRUE,
  all.missing = TRUE,
  len = NULL,
  min.len = NULL,
  max.len = NULL,
  unique = FALSE,
  names = NULL,
  null.ok = FALSE,
  .var.name = vname(x),
  add = NULL
)

testList(
  x,
  types = character(0L),
  any.missing = TRUE,
  all.missing = TRUE,
  len = NULL,
  min.len = NULL,
  max.len = NULL,
  unique = FALSE,
  names = NULL,
  null.ok = FALSE
)

test_list(
  x,
  types = character(0L),
  any.missing = TRUE,
  all.missing = TRUE,
  len = NULL,
  min.len = NULL,
  max.len = NULL,
  unique = FALSE,
  names = NULL,
  null.ok = FALSE
)

expect_list(
  x,
  types = character(0L),
  any.missing = TRUE,
  all.missing = TRUE,
  len = NULL,
  min.len = NULL,
  max.len = NULL,
  unique = FALSE,
  names = NULL,
  null.ok = FALSE,
  info = NULL,
  label = vname(x)
)

Arguments

`x`	[`any`] Object to check.
`types`	[`character`] Character vector of class names. Each list element must inherit from at least one of the provided types. The types “logical”, “integer”, “integerish”, “double”, “numeric”, “complex”, “character”, “factor”, “atomic”, “vector” “atomicvector”, “array”, “matrix”, “list”, “function”, “environment” and “null” are supported. For other types `inherits` is used as a fallback to check `x`'s inheritance. Defaults to `character(0)` (no check).
`any.missing`	[`logical(1)`] Are vectors with missing values allowed? Default is `TRUE`.
`all.missing`	[`logical(1)`] Are vectors with no non-missing values allowed? Default is `TRUE`. Note that empty vectors do not have non-missing values.
`len`	[`integer(1)`] Exact expected length of `x`.
`min.len`	[`integer(1)`] Minimal length of `x`.
`max.len`	[`integer(1)`] Maximal length of `x`.
`unique`	[`logical(1)`] Must all values be unique? Default is `FALSE`.
`names`	[`character(1)`] Check for names. See `checkNamed` for possible values. Default is “any” which performs no check at all. Note that you can use `checkSubset` to check for a specific set of names.
`null.ok`	[`logical(1)`] If set to `TRUE`, `x` may also be `NULL`. In this case only a type check of `x` is performed, all additional checks are disabled.
`.var.name`	[`character(1)`] Name of the checked object to print in assertions. Defaults to the heuristic implemented in `vname`.
`add`	[`AssertCollection`] Collection to store assertion messages. See `AssertCollection`.
`info`	[`character(1)`] Extra information to be included in the message for the testthat reporter. See `expect_that`.
`label`	[`character(1)`] Name of the checked object to print in messages. Defaults to the heuristic implemented in `vname`.

Value

Depending on the function prefix: If the check is successful, the functions assertList/assert_list return x invisibly, whereas checkList/check_list and testList/test_list return TRUE. If the check is not successful, assertList/assert_list throws an error message, testList/test_list returns FALSE, and checkList/check_list return a string with the error message. The function expect_list always returns an expectation.

Note

Contrary to R's is.list, objects of type data.frame and pairlist are not recognized as list.

Missingness is defined here as elements of the list being NULL, analogously to anyMissing.

The test for uniqueness does differentiate between the different NA types which are built-in in R. This is required to be consistent with unique while checking scalar missing values. Also see the example.

Examples

testList(list())
testList(as.list(iris), types = c("numeric", "factor"))

# Missingness
testList(list(1, NA), any.missing = FALSE)
testList(list(1, NULL), any.missing = FALSE)

# Uniqueness differentiates between different NA types:
testList(list(NA, NA), unique = TRUE)
testList(list(NA, NA_real_), unique = TRUE)

checkmate documentation built on Aug. 18, 2025, 5:36 p.m.