sequence

Module nu.forms.collections.abc.sequence.

Sequence collection: bases + mutations.

SequenceForm = Collection + Sliceable + first/last/index/count/reversed MutableSequenceForm = Sequence + append/insert/pop/extend/remove/reverse

Sorted/Reversed are standalone core atoms (nu.Sorted, nu.Reversed).

Follows Python's collections.abc.Sequence / MutableSequence pattern.

MutableSequenceForm

Base for in-place-mutable sequences, like collections.abc.MutableSequence.

MutableSequenceForm()

Path nu.forms.collections.abc.MutableSequenceForm.

Notes

• Every mutator here needs a Ref on the left; none of them evaluate standalone against a plain sequence value.
• pop is the one Action (mutates and returns a value); the rest are Commands (mutate, yield nothing).

Methods

.append(value)

Append value to the end of self.

Builds Any.

Arguments

Yields

Nothing (Command).

Notes

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

Undocumented: example.

.extend(other)

Extend self with the elements of other, in order.

Builds Any.

Arguments

Yields

Nothing (Command).

Notes

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

Undocumented: example.

.insert(index, value)

Insert value at index, shifting later elements right.

Builds Any.

Arguments

Yields

Nothing (Command).

Notes

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

Undocumented: example.

.pop(index=-1)

Remove and return the element at index.

Builds ElementResultT.

Arguments

Yields

The removed element (Action). EMPTY when index is out of range. An EMPTY self or index raises, as any write does.

Notes

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

Undocumented: example.

.del_at(index)

Remove the element at index.

Builds Any.

Arguments

Yields

Nothing (Command).

Notes

• Mutates self and needs a Ref on the left; it can't run standalone against a plain sequence value.
• Use this over pop when a Command is wanted instead of the Action pop yields.

Undocumented: example.

.remove(value, missing_ok=False)

Remove the first occurrence of value.

Builds Any.

Arguments

Yields

Nothing (Command).

Notes

• Mutates self and needs a Ref on the left; it can't run standalone against a plain sequence value.
• By default a value that isn't present raises at evaluation time, matching Python's list.remove.

Example

class Port(nu.Shape):
    tags = nu.ListRef.slot(str)
data = {"tags": ["a", "b", "a"]}
ctx = nu.Context().bind(dict, data, Port)
_ = nu.run(Port.tags.remove("a"), ctx)
_ = nu.run(Port.tags.remove("z", missing_ok=True), ctx)
data

{'tags': ['b', 'a']}

.reverse()

Reverse self in place.

Builds Any.

Yields

Nothing (Command).

Notes

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

Undocumented: example.

.sort()

Sort self in place, ascending, using the elements' natural order.

Builds Any.

Yields

Nothing (Command).

Notes

• No key support yet; sorting by a derived key is deferred.
• Mutates self and needs a Ref on the left; it can't run standalone against a plain sequence value.

Undocumented: example.

.copy()

Shallow copy of self: a new sequence with the same elements.

Builds CollectionResultT.

Yields

The copy. EMPTY when self is EMPTY.

Notes

• Unlike the mutators above, this is a Query: it doesn't mutate self and evaluates fine against a plain sequence value.

Example

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

[1, 2, 3]

.clear()

Remove every element from self.

Builds Any.

Yields

Nothing (Command).

Notes

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

Undocumented: example.

Inherited methods

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

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

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

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

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

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

From nu.lang.forms.Form:

From builtins.object:

Undocumented: example.

ReactiveSequenceForm

Sequence with change subscriptions layered on MutableSequenceForm.

ReactiveSequenceForm()

Path nu.forms.collections.abc.ReactiveSequenceForm.

Notes

• Adds on_change for any-change observation on this slot. The three tree-aware variants (on_child_change, on_children_change, on_descendants_change) are shape-domain and live on nu.domains.shape.collection.ReactiveCollectionForm, not here.

Methods

.on_change()

Subscribe to any change on this sequence slot.

Builds object.

Yields

An event stream firing whenever this slot changes.

Undocumented: example.

Inherited methods

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

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

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

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

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

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

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

From nu.lang.forms.Form:

From builtins.object:

Undocumented: example.

SequenceForm

Base for ordered, indexable values, like collections.abc.Sequence.

SequenceForm()

Path nu.forms.collections.abc.SequenceForm.

Notes

• Mixed in by List, Str, Bytes, Tuple, ListRef; this class only carries the shared shape. Concrete carriers narrow CollectionResultT/ElementResultT to their own types.
• Order is positional and stable: iteration, indexing, and first_elem/last_elem all agree on the same order.

Methods

a[key]

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

Builds ElementResultT | CollectionResultT.

Arguments

Yields

The element for an int key, the subsequence for a slice. EMPTY when self is EMPTY.

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, so a slice past the end yields a shorter (or empty) result rather than erroring.
• Negative indices and negative slice bounds work as in Python.

Examples

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

2

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

[2, 3]

.first_elem()

First element of self.

Builds ElementResultT.

Yields

The first element. EMPTY when self has no elements or is EMPTY.

Examples

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

1

nu.run(nu.List.of().first_elem())[0]

<EMPTY>

.last_elem()

Last element of self.

Builds ElementResultT.

Yields

The last element. EMPTY when self has no elements or is EMPTY.

Example

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

3

.index(value)

Lowest index in self where value is found, searching from the left.

Builds Int.

Arguments

Yields

The lowest matching index. EMPTY when self is EMPTY or value is not found.

Notes

• Unlike Python's list.index, a missing value does not raise: it yields EMPTY instead.

Examples

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

1

nu.run(nu.List.of(1, 2, 3).index(5))[0]

<EMPTY>

.count(value)

Count of occurrences of value in self.

Builds Int.

Arguments

Yields

The occurrence count, 0 when value is absent. EMPTY when self is EMPTY.

Example

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

2

.reversed()

Self walked back to front, as a stream.

Builds CollectionResultT.

Yields

The elements of self in reverse order.

Notes

• Yields a stream, not a materialized copy; consume it through a Flow (ForEachDo) or a Ref-backed context. It doesn't evaluate standalone as a scalar against a plain sequence value.

Undocumented: example.

Inherited methods

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

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

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

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

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

From nu.lang.forms.Form:

From builtins.object:

Undocumented: example.