Dict Methods

Dict methods are pure. Methods with mutating Python names return a new dict instead of changing the receiver.

Signatures

| Method | Returns | Notes | | --------------------- | --------------------------- | -------------------------------------------------- | | d.keys() | list | Keys in insertion order. | | d.values() | list | Values in insertion order. | | d.items() | list | Two-item key/value tuples in insertion order. | | d.copy() | dict | Shallow copy. | | d.clear() | dict | Empty dict. | | d.get(key) | value | err | Existing value, otherwise KeyError/NLK4003. | | d.get(key, default) | value | Existing value, otherwise default. | | d.pop(key) | tuple[value, dict] \| err | Removed value and new dict, or KeyError/NLK4003. | | d.pop(key, default) | tuple[value, dict] | Default and copied dict when absent. | | d.set(key, value) | dict | Dict with key set to value. | | d.remove(key) | dict \| err | Dict without key, or KeyError/NLK4003. | | d.update(other) | dict | Dict updated from a dict or list/tuple of pairs. |

Keys must be hashable. Updating an existing key replaces its value while preserving the key position. A new key is appended. Removing and then setting a key appends it at the end. update processes incoming entries in their iteration order: existing keys retain their positions and new keys appear at the end in first-seen order. Dict equality ignores insertion order.

items() returns a list of two-item tuples. Methods that look up, set, or remove keys require hashable keys. Use key in d and key not in d for membership.

Errors

pop(key) and remove(key) return KeyError/NLK4003 when the key is absent. update() accepts a dict or a list/tuple of two-item lists or tuples.

Raw dictionary indexing is fatal on a missing key. One-argument get(key) is the safe value-level alternative and returns KeyError/NLK4003; two-argument get(key, default) returns the default without a missing-key effect. A stored error returned by either form preserves its error identity and provenance.

pop(key, default) returns (default, copy) when the key is absent. update() rejects pair inputs unless every item is a two-item list or tuple.

Examples

counts = {"a": 1}
next_counts = counts.set("b", 2)
print(next_counts.keys())
print(next_counts.values())

value, rest = next_counts.pop("a") catch (0, next_counts)
print(value)
print(rest)

print(rest.update([["c", 3]]))