Convert Candidate from Cython to Python class.

setup.py

@@ -30,7 +30,6 @@ MOD_NAMES = [
     "spacy.lexeme",
     "spacy.vocab",
     "spacy.attrs",
-    "spacy.kb.candidate",
     "spacy.kb.kb",
     "spacy.kb.kb_in_memory",
     "spacy.ml.tb_framework",

spacy/kb/__init__.py

@@ -1,3 +1,5 @@
 from .kb import KnowledgeBase
 from .kb_in_memory import InMemoryLookupKB
-from .candidate import Candidate, get_candidates, get_candidates_batch
+from .candidate import Candidate
+
+__all__ = ["KnowledgeBase", "InMemoryLookupKB", "Candidate"]

spacy/kb/candidate.pxd

@@ -1,12 +0,0 @@
-from .kb cimport KnowledgeBase
-from libcpp.vector cimport vector
-from ..typedefs cimport hash_t
-
-# Object used by the Entity Linker that summarizes one entity-alias candidate combination.
-cdef class Candidate:
-    cdef readonly KnowledgeBase kb
-    cdef hash_t entity_hash
-    cdef float entity_freq
-    cdef vector[float] entity_vector
-    cdef hash_t alias_hash
-    cdef float prior_prob

spacy/kb/candidate.py

@@ -0,0 +1,109 @@
+import abc
+from typing import List, Union, Callable
+
+
+class BaseCandidate(abc.ABC):
+    """A `BaseCandidate` object refers to a textual mention (`alias`) that may or may not be resolved
+    to a specific `entity_id` from a Knowledge Base. This will be used as input for the entity_id linking
+    algorithm which will disambiguate the various candidates to the correct one.
+    Each candidate (alias, entity_id) pair is assigned a certain prior probability.
+
+    DOCS: https://spacy.io/api/kb/#candidate-init
+    """
+
+    def __init__(
+        self, mention: str, entity_id: Union[int, str], entity_vector: List[float]
+    ):
+        """Create new instance of `Candidate`. Note: has to be a sub-class, otherwise error will be raised.
+        mention (str): Mention text for this candidate.
+        entity_id (Union[int, str]): Unique entity ID.
+        entity_vector (List[float]): Entity embedding.
+        """
+        self._mention = mention
+        self._entity_id = entity_id
+        self._entity_vector = entity_vector
+
+    @property
+    def entity(self) -> Union[int, str]:
+        """RETURNS (Union[int, str]): Entity ID."""
+        return self._entity_id
+
+    @property
+    @abc.abstractmethod
+    def entity_(self) -> str:
+        """RETURNS (str): Entity name."""
+
+    @property
+    def mention(self) -> str:
+        """RETURNS (str): Mention."""
+        return self._mention
+
+    @property
+    def entity_vector(self) -> List[float]:
+        """RETURNS (List[float]): Entity vector."""
+        return self._entity_vector
+
+
+class Candidate(BaseCandidate):
+    """`Candidate` for InMemoryLookupKBCandidate."""
+
+    def __init__(
+        self,
+        retrieve_string_from_hash: Callable[[int], str],
+        entity_hash: int,
+        entity_freq: int,
+        entity_vector: List[float],
+        alias_hash: int,
+        prior_prob: float,
+    ):
+        """
+        retrieve_string_from_hash (Callable[[int], str]): Callable retrieveing entity name from provided entity/vocab
+            hash.
+        entity_hash (str): Hashed entity name /ID.
+        entity_freq (int): Entity frequency in KB corpus.
+        entity_vector (List[float]): Entity embedding.
+        alias_hash (int): Hashed alias.
+        prior_prob (float): Prior probability of entity for this mention - i.e. the probability that, independent of
+            the context, this mention resolves to this entity_id in the corpus used to build the knowledge base. In
+            cases in which this isn't always possible (e.g.: the corpus to analyse contains mentions that the KB corpus
+            doesn't) it might be better to eschew this information and always supply the same value.
+        """
+        super().__init__(
+            mention=retrieve_string_from_hash(alias_hash),
+            entity_id=entity_hash,
+            entity_vector=entity_vector,
+        )
+        self._retrieve_string_from_hash = retrieve_string_from_hash
+        self._entity_hash = entity_hash
+        self._entity_freq = entity_freq
+        self._alias_hash = alias_hash
+        self._prior_prob = prior_prob
+
+    @property
+    def entity(self) -> int:
+        """RETURNS (int): hash of the entity_id's KB ID/name"""
+        return self._entity_hash
+
+    @property
+    def entity_(self) -> str:
+        """RETURNS (str): ID/name of this entity_id in the KB"""
+        return self._retrieve_string_from_hash(self._entity_hash)
+
+    @property
+    def alias(self) -> int:
+        """RETURNS (int): hash of the alias"""
+        return self._alias_hash
+
+    @property
+    def alias_(self) -> str:
+        """RETURNS (str): ID of the original alias"""
+        return self._retrieve_string_from_hash(self._alias_hash)
+
+    @property
+    def entity_freq(self) -> float:
+        return self._entity_freq
+
+    @property
+    def prior_prob(self) -> float:
+        """RETURNS (List[float]): Entity vector."""
+        return self._prior_prob

spacy/kb/candidate.pyx

@@ -1,74 +0,0 @@
-# cython: infer_types=True, profile=True
-
-from typing import Iterable
-from .kb cimport KnowledgeBase
-from ..tokens import Span
-
-cdef class Candidate:
-    """A `Candidate` object refers to a textual mention (`alias`) that may or may not be resolved
-    to a specific `entity` from a Knowledge Base. This will be used as input for the entity linking
-    algorithm which will disambiguate the various candidates to the correct one.
-    Each candidate (alias, entity) pair is assigned a certain prior probability.
-
-    DOCS: https://spacy.io/api/kb/#candidate-init
-    """
-
-    def __init__(self, KnowledgeBase kb, entity_hash, entity_freq, entity_vector, alias_hash, prior_prob):
-        self.kb = kb
-        self.entity_hash = entity_hash
-        self.entity_freq = entity_freq
-        self.entity_vector = entity_vector
-        self.alias_hash = alias_hash
-        self.prior_prob = prior_prob
-
-    @property
-    def entity(self) -> int:
-        """RETURNS (uint64): hash of the entity's KB ID/name"""
-        return self.entity_hash
-
-    @property
-    def entity_(self) -> str:
-        """RETURNS (str): ID/name of this entity in the KB"""
-        return self.kb.vocab.strings[self.entity_hash]
-
-    @property
-    def alias(self) -> int:
-        """RETURNS (uint64): hash of the alias"""
-        return self.alias_hash
-
-    @property
-    def alias_(self) -> str:
-        """RETURNS (str): ID of the original alias"""
-        return self.kb.vocab.strings[self.alias_hash]
-
-    @property
-    def entity_freq(self) -> float:
-        return self.entity_freq
-
-    @property
-    def entity_vector(self) -> Iterable[float]:
-        return self.entity_vector
-
-    @property
-    def prior_prob(self) -> float:
-        return self.prior_prob
-
-
-def get_candidates(kb: KnowledgeBase, mention: Span) -> Iterable[Candidate]:
-    """
-    Return candidate entities for a given mention and fetching appropriate entries from the index.
-    kb (KnowledgeBase): Knowledge base to query.
-    mention (Span): Entity mention for which to identify candidates.
-    RETURNS (Iterable[Candidate]): Identified candidates.
-    """
-    return kb.get_candidates(mention)
-
-
-def get_candidates_batch(kb: KnowledgeBase, mentions: Iterable[Span]) -> Iterable[Iterable[Candidate]]:
-    """
-    Return candidate entities for the given mentions and fetching appropriate entries from the index.
-    kb (KnowledgeBase): Knowledge base to query.
-    mention (Iterable[Span]): Entity mentions for which to identify candidates.
-    RETURNS (Iterable[Iterable[Candidate]]): Identified candidates.
-    """
-    return kb.get_candidates_batch(mentions)

spacy/kb/kb_in_memory.pyx

@@ -238,14 +238,18 @@ cdef class InMemoryLookupKB(KnowledgeBase):
         alias_index = <int64_t>self._alias_index.get(alias_hash)
         alias_entry = self._aliases_table[alias_index]
 
-        return [Candidate(kb=self,
+        return [
+            Candidate(
+                retrieve_string_from_hash=self.vocab.strings.__getitem__,
                 entity_hash=self._entries[entry_index].entity_hash,
                 entity_freq=self._entries[entry_index].freq,
                 entity_vector=self._vectors_table[self._entries[entry_index].vector_index],
                 alias_hash=alias_hash,
-                          prior_prob=prior_prob)
+                prior_prob=prior_prob
+            )
             for (entry_index, prior_prob) in zip(alias_entry.entry_indices, alias_entry.probs)
-                if entry_index != 0]
+            if entry_index != 0
+        ]
 
     def get_vector(self, str entity):
         cdef hash_t entity_hash = self.vocab.strings[entity]

spacy/ml/models/entity_linker.py

@@ -6,7 +6,7 @@ from thinc.api import Model, Maxout, Linear, tuplify, Ragged
 
 from ...util import registry
 from ...kb import KnowledgeBase, InMemoryLookupKB
-from ...kb import Candidate, get_candidates, get_candidates_batch
+from ...kb import Candidate
 from ...vocab import Vocab
 from ...tokens import Span, Doc
 from ..extract_spans import extract_spans
@@ -109,3 +109,23 @@ def create_candidates_batch() -> Callable[
     [KnowledgeBase, Iterable[Span]], Iterable[Iterable[Candidate]]
 ]:
     return get_candidates_batch
+
+
+def get_candidates(kb: KnowledgeBase, mention: Span) -> Iterable[Candidate]:
+    """
+    Return candidate entities for a given mention and fetching appropriate entries from the index.
+    kb (KnowledgeBase): Knowledge base to query.
+    mention (Span): Entity mention for which to identify candidates.
+    RETURNS (Iterable[Candidate]): Identified candidates.
+    """
+    return kb.get_candidates(mention)
+
+
+def get_candidates_batch(kb: KnowledgeBase, mentions: Iterable[Span]) -> Iterable[Iterable[Candidate]]:
+    """
+    Return candidate entities for the given mentions and fetching appropriate entries from the index.
+    kb (KnowledgeBase): Knowledge base to query.
+    mention (Iterable[Span]): Entity mentions for which to identify candidates.
+    RETURNS (Iterable[Iterable[Candidate]]): Identified candidates.
+    """
+    return kb.get_candidates_batch(mentions)

spacy/tests/pipeline/test_entity_linker.py

@@ -7,10 +7,10 @@ from thinc.types import Ragged
 from spacy import registry, util
 from spacy.attrs import ENT_KB_ID
 from spacy.compat import pickle
-from spacy.kb import Candidate, InMemoryLookupKB, get_candidates, KnowledgeBase
+from spacy.kb import Candidate, InMemoryLookupKB, KnowledgeBase
 from spacy.lang.en import English
 from spacy.ml import load_kb
-from spacy.ml.models.entity_linker import build_span_maker
+from spacy.ml.models.entity_linker import build_span_maker, get_candidates
 from spacy.pipeline import EntityLinker, TrainablePipe
 from spacy.pipeline.tok2vec import DEFAULT_TOK2VEC_MODEL
 from spacy.scorer import Scorer