collections.list

Module nu.forms.collections.list_.

List - list interface.

Name	Sort	Call	Meaning
List	`scalar_query`	`List()`	List interface. Mutable sequence + comparable.

List

List interface. Mutable sequence + comparable.

List()

Path nu.forms.List. Kind ScalarQuery, sort scalar_query, cardinality scalar.

Notes

+ concatenates and * repeats, matching Python's list operators. There's no other arithmetic.
Comparison operators compare element-by-element, Python list ordering, and yield Bool. Chained comparisons like a > b > c do not build a single term; write them as And(a > b, b > c).
Indexing with an out-of-range int raises at evaluation time, matching Python. Slicing never raises; out-of-range bounds clamp like Python slicing.
Subscript write/delete (self[i] = v, del self[i]) mutate in place and need a Ref on the left, not a plain List value - they can't run standalone.

Example

nu.run(nu.List.of(1, 2) + nu.List.of(3, 4))[0]

[1, 2, 3, 4]

Methods

`List.create()`

Yield a fresh empty list.

Builds List[T].

Yields

An empty list.

Example

nu.run(nu.List.create())[0]

[]

`List.of(items)`

Yield a list from positional item expressions.

Builds List.

Arguments

Name	Type	Default	Meaning
`items`			the item expressions, packed into the list in order. Each may be a Nu expression or a plain literal.

Yields

The list [<items[0]>, <items[1]>, ...]. INVALID when any item resolves to a sentinel.

Notes

Sibling to Tuple.of, same evaluation shape, different wrapping.

Example

nu.run(nu.List.of(1, 2, 3))[0]

[1, 2, 3]

`a[key]`

Element at an int index, or subsequence for a slice.

Arguments

Name	Type	Default	Meaning
`key`			an int index, or a Python slice of int start/stop/step.

Yields

The element for an int key, the sublist for a slice. INVALID when self is a sentinel or not a List.

Notes

An out-of-range int index raises at evaluation time, matching Python. A slice never raises; out-of-range bounds clamp like Python slicing.
Negative indices and negative slice bounds work as in Python.
When T is a known primitive (bool, int, float, str, bytes), the overloads above narrow the int-index result to that Form's type for the type checker; anything else falls back to Any.

Examples

nu.run(nu.List.of(1, 2, 3)[1])[0]

nu.run(nu.List.of(1, 2, 3)[1:3])[0]

[2, 3]

`a + b`

Concatenation of self and other.

Builds List[T].

Arguments

Name	Type	Default	Meaning
`other`	`ListArg[T]`		the list to append to self.

Yields

The concatenation. INVALID when either operand is not a List or is a sentinel.

Example

nu.run(nu.List.of(1, 2) + nu.List.of(3, 4))[0]

[1, 2, 3, 4]

`a * b`

Self repeated n times.

Builds List[T].

Arguments

Name	Type	Default	Meaning
`n`	`IntArg`		the repeat count. `0` or negative yields an empty list.

Yields

The repeated list. INVALID when self is a sentinel or not a List.

Example

nu.run(nu.List.of(1, 2) * 3)[0]

[1, 2, 1, 2, 1, 2]

`a[key] = value`

Subscript write: self[index] = value.

Builds Any.

Arguments

Name	Type	Default	Meaning
`index`	`IntArg`		the position to write to. An out-of-range index raises at evaluation time, matching Python.
`value`	`Arg[T]`		the value to store at index.

Yields

Nothing (Command).

Notes

Mutates self and needs a Ref on the left; it can't run standalone against a plain List value.

Undocumented: example.

`a > b`

Self strictly greater than other, element-by-element.

Builds Bool.

Arguments

Name	Type	Default	Meaning
`other`	`ListArg[T]`		the list to compare against.

Yields

True when self sorts after other, False otherwise. INVALID when either operand is not a List or is a sentinel.

Example

nu.run(nu.List.of(1, 3) > nu.List.of(1, 2))[0]

True

`a < b`

Self strictly less than other, element-by-element.

Builds Bool.

Arguments

Name	Type	Default	Meaning
`other`	`ListArg[T]`		the list to compare against.

Yields

True when self sorts before other, False otherwise. INVALID when either operand is not a List or is a sentinel.

Example

nu.run(nu.List.of(1, 2) < nu.List.of(1, 3))[0]

True

`a >= b`

Self greater than or equal to other, element-by-element.

Builds Bool.

Arguments

Name	Type	Default	Meaning
`other`	`ListArg[T]`		the list to compare against.

Yields

True when self sorts after or equal to other, False otherwise. INVALID when either operand is not a List or is a sentinel.

Example

nu.run(nu.List.of(1, 2) >= nu.List.of(1, 2))[0]

True

`a <= b`

Self less than or equal to other, element-by-element.

Builds Bool.

Arguments

Name	Type	Default	Meaning
`other`	`ListArg[T]`		the list to compare against.

Yields

True when self sorts before or equal to other, False otherwise. INVALID when either operand is not a List or is a sentinel.

Example

nu.run(nu.List.of(1, 2) <= nu.List.of(1, 3))[0]

True

`a == b`

Self equal to other by value.

Builds Bool.

Arguments

Name	Type	Default	Meaning
`other`	`ListArg[T]`		the list to compare against.

Yields

True when the lists compare equal, False otherwise. INVALID when either operand is not a List or is a sentinel.

Notes

Value equality, not identity. Use is_ for identity.

Example

nu.run(nu.List.of(1, 2) == nu.List.of(1, 2))[0]

True

`a != b`

Self not equal to other by value.

Builds Bool.

Arguments

Name	Type	Default	Meaning
`other`	`ListArg[T]`		the list to compare against.

Yields

True when the lists differ, False otherwise. INVALID when either operand is not a List or is a sentinel.

Notes

Value inequality, not identity. Use is_ for identity.

Example

nu.run(nu.List.of(1, 2) != nu.List.of(1, 3))[0]

True

`.is_(other)`

Identity comparison: self is other.

Builds Bool.

Arguments

Name	Type	Default	Meaning
`other`	`ListArg[T]`		the value to compare identity against.

Yields

True when self and other evaluate to the same Python object, False otherwise.

Notes

Object identity, not value equality. For value comparison use == instead. Two lists built separately with equal elements are not the same object.

Example

nu.run(nu.List.of(1, 2).is_(nu.List.of(1, 2)))[0]

False

Inherited methods

From nu.forms.collections.abc.sequence.MutableSequenceForm:

Call	Builds	Meaning
`.append(value)`	`Any`	Append value to the end of self.
`.extend(other)`	`Any`	Extend self with the elements of other, in order.
`.insert(index, value)`	`Any`	Insert value at index, shifting later elements right.
`.pop(index=-1)`	`ElementResultT`	Remove and return the element at index.
`.del_at(index)`	`Any`	Remove the element at index.
`.remove(value)`	`Any`	Remove the first occurrence of value.
`.reverse()`	`Any`	Reverse self in place.
`.sort()`	`Any`	Sort self in place, ascending, using the elements' natural order.
`.copy()`	`CollectionResultT`	Shallow copy of self: a new sequence with the same elements.
`.clear()`	`Any`	Remove every element from self.

From nu.forms.collections.abc.sequence.SequenceForm:

Call	Builds	Meaning
`.first_elem()`	`ElementResultT`	First element of self.
`.last_elem()`	`ElementResultT`	Last element of self.
`.index(value)`	`Int`	Lowest index in self where value is found, searching from the left.
`.count(value)`	`Int`	Count of occurrences of value in self.
`.reversed()`	`CollectionResultT`	Self walked back to front, as a stream.

From nu.forms.collections.abc.collection.CollectionForm:

Call	Builds	Meaning
`.extract()`	`object`	Materialise the full subtree rooted at self.

From nu.forms.collections.abc.sized.SizedForm:

Call	Builds	Meaning
`.len()`	`Int`	Length of self.

From nu.forms.collections.abc.iterable.IterableForm:

Call	Builds	Meaning
`iter(a)`	`Iterator[ElementT]`	Open self into a lazy iterator stream (Python's `iter`).

From nu.forms.collections.abc.container.ContainerForm:

Call	Builds	Meaning
`.contains(item)`	`Bool`	Whether item is a member of self.

From nu.forms.collections.abc.sliceable.SliceableForm:

Call	Builds	Meaning
`.slice(start, stop, step=None)`	`ResultT`	Slice of self from start to stop, stepping by step.

From nu.lang.forms.Form:

Call	Builds	Meaning
`.is_empty()`	`Bool`	True if this Form yields the EMPTY sentinel.
`.is_invalid()`	`Bool`	True if this Form yields the INVALID sentinel.
`.is_sentinel()`	`Bool`	True if this Form yields either sentinel (EMPTY or INVALID).
`.not_empty()`	`Bool`	True if this Form does not yield EMPTY.
`.not_invalid()`	`Bool`	True if this Form does not yield INVALID.

collections.list_

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