constantdict API reference

class constantdict.constantdict

An immutable dictionary that does not allow modifications after creation. This class behaves mostly like a dict, but with the following differences.

Additional methods compared to dict

__hash__() → int

Return a hash of this constantdict. This constantdict is hashable if all of its keys and values are hashable. Once computed, the hash is cached.

mutate() → constantdictmutation[K, V]

Return a mutable copy of this constantdict as a constantdictmutation.

Run constantdictmutation.finish() to convert back to an immutable constantdict.

Note

Based on the immutables.Map API.

>>> cd = constantdict(a=1, b=2)
>>> cd_mut = cd.mutate()
>>> cd_mut["a"] = 10
>>> del cd_mut["b"]
>>> cd_new = cd_mut.finish()
>>> cd_new
constantdict({'a': 10})
>>> cd  # unchanged
constantdict({'a': 1, 'b': 2})

A constantdictmutation can also be used as a context manager:

>>> with constantdict(a=1, b=2).mutate() as cd_mut:
...     cd_mut["a"] = 10
...     del cd_mut["b"]
...     cd_new = cd_mut.finish()
>>> cd_new
constantdict({'a': 10})

Methods that return a modified copy of a constantdict

set(key: K, value: Any) → constantdict[K, V]

Return a new constantdict with the item at key set to val.

setdefault(key: K, default: V | None = None) → constantdict[K, V]

Return a new constantdict with the item at key set to default if key is not in the dictionary.

Return a reference to itself if key is present.

Note

Based on the frozendict API.

delete(key: K) → constantdict[K, V]

Return a new constantdict without the item at key.

Raise a KeyError if key is not present.

update(other: dict[K, V]) → constantdict[K, V]

Return a new constantdict with updated items from other.

Note

In contrast to dict.update(), this method does not modify the original constantdict, but creates a new, updated copy.

>>> cd = constantdict(a=1, b=2)
>>> cd_new = cd.update({"a": 10, "c": 3})
>>> cd_new
constantdict({'a': 10, 'b': 2, 'c': 3})
>>> cd
constantdict({'a': 1, 'b': 2})

discard(key: K) → constantdict[K, V]

Return a new constantdict without the item at the given key.

Return a reference to itself if the key is not present.

Note

Based on the pyrsistent.PMap API.

Deleted methods compared to dict

These methods raise an AttributeError when called.

__delitem__()

__setitem__()

clear()

popitem()

pop()

class constantdict.constantdictmutation

A mutable dictionary that can be converted back to a constantdict without copying. This class behaves exactly like a dict, except for the addition mentioned below.

Additional method compared to dict

finish() → constantdict[K, V]

Convert this object to an immutable version of itself.

>>> cd_mut = constantdict(a=1, b=2).mutate()
>>> cd_mut["a"] = 12
>>> cd = cd_mut.finish()
>>> cd
constantdict({'a': 12, 'b': 2})

class constantdict.constantdictuncachedhash

A constantdict that does not cache its hash value. This is useful when the dictionary contains items that are not immutable and whose hash value might therefore change. This class behaves exactly like a constantdict in all other respects.

class constantdict.constantdictuncachedhashmutation

A mutable dictionary that can be converted back to a constantdictuncachedhash without copying. This class behaves exactly like a constantdictmutation in all other respects.

Type classes

class constantdict.K

A type representing a key in a constantdict. Must be hashable.

class constantdict.V

A (covariant) type representing a value in a constantdict.