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dotfiles/python/ebook_search/protected_phrases/extraction.py
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Python

"""Candidate phrase extraction and scoring for protected phrases."""
from __future__ import annotations
import logging
import re
from collections import defaultdict
from functools import lru_cache
from time import perf_counter
from typing import TYPE_CHECKING, Protocol
from yake import KeywordExtractor
from python.ebook_search.protected_phrases.config import (
get_bad_ends,
get_bad_starts,
get_ignored_phrases,
get_most_common_words,
)
from python.ebook_search.protected_phrases.models import PhraseCandidate
from python.ebook_search.protected_phrases.text_normalization import tokenize, tokenize_with_offsets
if TYPE_CHECKING:
from collections.abc import Iterable, Mapping, Sequence
from python.ebook_search.config import EbookSearchConfig
logger = logging.getLogger(__name__)
BAD_START_SCORE_PENALTY = 3.0
BAD_END_SCORE_PENALTY = 3.0
SOURCE_FIELDS = (
"source_raw_ngram",
"source_yake",
"source_spacy_ner",
"source_spacy_noun_chunk",
"source_capitalized",
"source_metadata",
)
CAPITALIZED_PHRASE_RE = re.compile(r"\b(?:[A-Z][a-zA-Z']+)(?:\s+(?:of|the|and|in|on|for|[A-Z][a-zA-Z']+)){0,6}")
class SpacySpan(Protocol):
"""Small protocol for the spaCy span attributes used by this module."""
text: str
class SpacyEntity(SpacySpan, Protocol):
"""Small protocol for the spaCy entity attributes used by this module."""
label_: str
class SpacyDoc(Protocol):
"""Small protocol for the spaCy doc attributes used by this module."""
ents: Iterable[SpacyEntity]
noun_chunks: Iterable[SpacySpan]
class SpacyLanguage(Protocol):
"""Small protocol for a callable spaCy language pipeline."""
def __call__(self, text: str) -> SpacyDoc:
"""Parse text into a spaCy-like doc."""
class YakeExtractor(Protocol):
"""Small protocol for the YAKE extractor used by this module."""
def extract_keywords(self, text: str) -> Iterable[tuple[str, float]]:
"""Return YAKE keyword tuples."""
class YakeExtractorFactory(Protocol):
"""Callable constructor protocol for YAKE keyword extractors."""
def __call__(self, *, lan: str, n: int, dedupLim: float, top: int) -> YakeExtractor: # noqa: N803
"""Create a YAKE keyword extractor.
Args:
lan (str): Language code passed to YAKE.
n (int): Maximum n-gram size to extract.
dedupLim (float): Deduplication similarity threshold.
top (int): Maximum number of keyphrases to return.
Returns:
YakeExtractor: The constructed keyword extractor.
"""
def strip_leading_articles(phrase_norm: str) -> str:
"""Remove one leading English article from a normalized phrase.
Args:
phrase_norm (str): Normalized phrase text to strip.
Returns:
str: The phrase with a single leading ``the``, ``a``, or ``an`` removed.
"""
tokens_ = phrase_norm.split()
if tokens_ and tokens_[0] in {"the", "a", "an"}:
tokens_ = tokens_[1:]
return " ".join(tokens_)
def normalize_candidate_phrase(
phrase_text: str,
config: EbookSearchConfig,
*,
min_tokens: int | None = None,
max_tokens: int | None = None,
strip_leading_article: bool = False,
) -> tuple[str, str, int] | None:
"""Normalize a candidate phrase and validate token bounds.
Args:
phrase_text (str): Raw phrase text to normalize.
config (EbookSearchConfig): Runtime phrase-tuning settings.
min_tokens (int | None): Minimum token count override; defaults to ``config.phrase_min_tokens``.
max_tokens (int | None): Maximum token count override; defaults to ``config.phrase_max_tokens``.
strip_leading_article (bool): Whether to drop a single leading English article.
Returns:
tuple[str, str, int] | None: Display text, normalized phrase, and token count, or ``None``
when the phrase falls outside the token bounds or is ignored.
"""
normalized_tokens = tokenize_with_offsets(phrase_text)
start = 0
if strip_leading_article and normalized_tokens and normalized_tokens[0].text in {"the", "a", "an"}:
start = 1
selected_tokens = normalized_tokens[start:]
min_count = config.phrase_min_tokens if min_tokens is None else min_tokens
max_count = config.phrase_max_tokens if max_tokens is None else max_tokens
if len(selected_tokens) < min_count or len(selected_tokens) > max_count:
return None
phrase_norm = " ".join(token.text for token in selected_tokens)
if phrase_norm in get_ignored_phrases():
return None
display_text = phrase_text[selected_tokens[0].start_char : selected_tokens[-1].end_char].strip()
return display_text or phrase_norm, phrase_norm, len(selected_tokens)
def extract_raw_ngrams(text: str, config: EbookSearchConfig) -> dict[str, PhraseCandidate]:
"""Extract raw normalized n-grams as high-recall candidates.
Args:
text (str): Book text to slide n-gram windows over.
config (EbookSearchConfig): Runtime phrase-tuning settings.
Returns:
dict[str, PhraseCandidate]: Candidates keyed by normalized phrase, with raw counts.
"""
tokens_ = tokenize(text)
out: dict[str, PhraseCandidate] = {}
for ngram_size in range(config.phrase_min_tokens, config.phrase_max_tokens + 1):
for start in range(len(tokens_) - ngram_size + 1):
normalized = normalize_candidate_phrase(" ".join(tokens_[start : start + ngram_size]), config)
if normalized is None:
continue
phrase_text, phrase_norm, token_count = normalized
item = out.setdefault(
phrase_norm,
PhraseCandidate(
phrase_text=phrase_text,
phrase_norm=phrase_norm,
token_count=token_count,
source_raw_ngram=True,
),
)
item.raw_count += 1
return out
@lru_cache(maxsize=2)
def get_yake_extractor(max_ngram: int, top_k: int) -> KeywordExtractor:
"""Return a cached YAKE extractor for the given settings.
Constructing a ``KeywordExtractor`` loads the language's stopword list from disk, so it is
cached and reused across books rather than rebuilt on every call.
Args:
max_ngram (int): Maximum n-gram size to extract.
top_k (int): Maximum number of keyphrases to request.
Returns:
KeywordExtractor: A shared extractor instance for the given settings.
"""
return KeywordExtractor(lan="en", n=max_ngram, dedupLim=0.85, top=top_k)
def extract_yake_candidates(
book_text: str,
config: EbookSearchConfig,
top_k: int = 1000,
) -> dict[str, PhraseCandidate]:
"""Extract YAKE keyphrases when the optional YAKE package is installed.
Args:
book_text (str): Full book text to extract keyphrases from.
config (EbookSearchConfig): Runtime phrase-tuning settings.
top_k (int): Maximum number of YAKE keyphrases to request.
Returns:
dict[str, PhraseCandidate]: Candidates keyed by normalized phrase, with YAKE scores.
"""
extractor = get_yake_extractor(config.phrase_max_tokens, top_k)
out: dict[str, PhraseCandidate] = {}
for phrase_text, yake_score in extractor.extract_keywords(book_text):
normalized = normalize_candidate_phrase(phrase_text, config)
if normalized is None:
continue
display_text, phrase_norm, token_count = normalized
out[phrase_norm] = PhraseCandidate(
phrase_text=display_text,
phrase_norm=phrase_norm,
token_count=token_count,
source_yake=True,
yake_score=float(yake_score),
)
return out
def extract_spacy_candidates(
book_text: str,
nlp: SpacyLanguage,
config: EbookSearchConfig,
) -> dict[str, PhraseCandidate]:
"""Extract spaCy named entities and noun chunks from one text block.
Args:
book_text (str): Text block to parse with spaCy.
nlp (SpacyLanguage): Callable spaCy language pipeline.
config (EbookSearchConfig): Runtime phrase-tuning settings.
Returns:
dict[str, PhraseCandidate]: Candidates keyed by normalized phrase from entities and noun chunks.
"""
out: dict[str, PhraseCandidate] = {}
doc = nlp(book_text)
for ent in doc.ents:
normalized = normalize_candidate_phrase(
ent.text,
config,
max_tokens=config.phrase_max_entity_tokens,
)
if normalized is None:
continue
phrase_text, phrase_norm, token_count = normalized
out[phrase_norm] = PhraseCandidate(
phrase_text=phrase_text,
phrase_norm=phrase_norm,
token_count=token_count,
source_spacy_ner=True,
spacy_label=ent.label_,
)
for chunk in doc.noun_chunks:
normalized = normalize_candidate_phrase(chunk.text, config, strip_leading_article=True)
if normalized is None:
continue
phrase_text, phrase_norm, token_count = normalized
out[phrase_norm] = PhraseCandidate(
phrase_text=phrase_text,
phrase_norm=phrase_norm,
token_count=token_count,
source_spacy_noun_chunk=True,
)
return out
def extract_capitalized_phrases(original_text: str, config: EbookSearchConfig) -> dict[str, PhraseCandidate]:
"""Extract capitalized phrase runs that often carry fictional terms.
Args:
original_text (str): Original-case book text to scan for capitalized runs.
config (EbookSearchConfig): Runtime phrase-tuning settings.
Returns:
dict[str, PhraseCandidate]: Candidates keyed by normalized phrase from capitalized runs.
"""
out: dict[str, PhraseCandidate] = {}
for match in CAPITALIZED_PHRASE_RE.finditer(original_text):
phrase_text = match.group(0).strip()
normalized = normalize_candidate_phrase(
phrase_text,
config,
max_tokens=config.phrase_max_entity_tokens,
)
if normalized is None:
continue
display_text, phrase_norm, token_count = normalized
out[phrase_norm] = PhraseCandidate(
phrase_text=display_text,
phrase_norm=phrase_norm,
token_count=token_count,
source_capitalized=True,
)
return out
def extract_metadata_candidates(
metadata: Mapping[str, object] | None,
config: EbookSearchConfig,
) -> dict[str, PhraseCandidate]:
"""Extract phrases from book metadata values such as title, author, and series.
Args:
metadata (Mapping[str, object] | None): Book metadata values, or ``None`` when unavailable.
config (EbookSearchConfig): Runtime phrase-tuning settings.
Returns:
dict[str, PhraseCandidate]: Candidates keyed by normalized phrase from metadata values.
"""
if metadata is None:
return {}
out: dict[str, PhraseCandidate] = {}
for value in metadata.values():
if value is None:
continue
phrase_text = str(value).strip()
normalized = normalize_candidate_phrase(
phrase_text,
config,
max_tokens=config.phrase_max_entity_tokens,
)
if normalized is None:
continue
display_text, phrase_norm, token_count = normalized
out[phrase_norm] = PhraseCandidate(
phrase_text=display_text,
phrase_norm=phrase_norm,
token_count=token_count,
source_metadata=True,
)
return out
def merge_candidate_sources(*sources: Mapping[str, PhraseCandidate]) -> dict[str, PhraseCandidate]:
"""Merge candidate dictionaries by normalized phrase.
Args:
*sources (Mapping[str, PhraseCandidate]): Candidate maps to combine, keyed by normalized phrase.
Returns:
dict[str, PhraseCandidate]: One merged candidate per normalized phrase.
"""
merged: dict[str, PhraseCandidate] = {}
for source in sources:
for phrase_norm, item in source.items():
existing = merged.setdefault(
phrase_norm,
PhraseCandidate(
phrase_text=item.phrase_text,
phrase_norm=phrase_norm,
token_count=item.token_count,
),
)
merge_candidate(existing, item)
return merged
def merge_candidate(existing: PhraseCandidate, item: PhraseCandidate) -> None:
"""Merge one candidate into an existing candidate object.
Args:
existing (PhraseCandidate): Candidate mutated in place to absorb ``item``.
item (PhraseCandidate): Candidate whose sources, counts, and scores are merged in.
"""
existing.source_raw_ngram = existing.source_raw_ngram or item.source_raw_ngram
existing.source_yake = existing.source_yake or item.source_yake
existing.source_spacy_ner = existing.source_spacy_ner or item.source_spacy_ner
existing.source_spacy_noun_chunk = existing.source_spacy_noun_chunk or item.source_spacy_noun_chunk
existing.source_capitalized = existing.source_capitalized or item.source_capitalized
existing.source_metadata = existing.source_metadata or item.source_metadata
existing.raw_count += item.raw_count
if item.yake_score is not None:
existing.yake_score = item.yake_score
if item.spacy_label:
existing.spacy_label = item.spacy_label
def enrich_with_frequency_and_chapter_counts(
candidates: Mapping[str, PhraseCandidate],
chapters: Sequence[str],
) -> dict[str, PhraseCandidate]:
"""Add raw occurrence and chapter-spread counts to candidates.
Args:
candidates (Mapping[str, PhraseCandidate]): Candidates to enrich, keyed by normalized phrase.
chapters (Sequence[str]): Chapter-like text blocks used to count occurrences and spread.
Returns:
dict[str, PhraseCandidate]: Candidates with updated ``raw_count`` and ``chapter_count`` values.
"""
if not candidates:
return {}
candidate_sets_by_size: dict[int, set[str]] = defaultdict(set)
for phrase_norm, candidate in candidates.items():
candidate_sets_by_size[candidate.token_count].add(phrase_norm)
total_counts: defaultdict[str, int] = defaultdict(int)
chapter_counts: defaultdict[str, int] = defaultdict(int)
for chapter in chapters:
seen_in_chapter: set[str] = set()
chapter_tokens = tokenize(chapter)
for ngram_size, candidate_norms in candidate_sets_by_size.items():
for start in range(len(chapter_tokens) - ngram_size + 1):
phrase_norm = " ".join(chapter_tokens[start : start + ngram_size])
if phrase_norm not in candidate_norms:
continue
total_counts[phrase_norm] += 1
seen_in_chapter.add(phrase_norm)
for phrase_norm in seen_in_chapter:
chapter_counts[phrase_norm] += 1
enriched = dict(candidates)
for phrase_norm, candidate in enriched.items():
candidate.raw_count = max(candidate.raw_count, total_counts[phrase_norm])
candidate.chapter_count = chapter_counts[phrase_norm]
return enriched
def filter_storable_candidates(
candidates: Mapping[str, PhraseCandidate],
config: EbookSearchConfig,
) -> tuple[dict[str, PhraseCandidate], int, int, int]:
"""Remove candidates that should not be persisted.
Args:
candidates (Mapping[str, PhraseCandidate]): Candidates to filter, keyed by normalized phrase.
config (EbookSearchConfig): Runtime phrase-tuning settings.
Returns:
tuple[dict[str, PhraseCandidate], int, int, int]: The storable candidates followed by the counts
dropped for being too short, too rare, and too common.
"""
min_raw_count = minimum_candidate_raw_count(config)
filtered: dict[str, PhraseCandidate] = {}
too_short = 0
too_rare = 0
too_common = 0
for phrase_norm, candidate in candidates.items():
if candidate.token_count < config.phrase_min_tokens:
too_short += 1
continue
if candidate.raw_count < min_raw_count:
too_rare += 1
continue
if is_most_common_word_phrase(phrase_norm):
too_common += 1
continue
filtered[phrase_norm] = candidate
return filtered, too_short, too_rare, too_common
def minimum_candidate_raw_count(config: EbookSearchConfig) -> int:
"""Return the minimum occurrence count required before storing a candidate.
Args:
config (EbookSearchConfig): Runtime phrase-tuning settings.
Returns:
int: The minimum raw occurrence count, never less than 1.
"""
return max(config.phrase_raw_ngram_min_count, 1)
def is_most_common_word_phrase(phrase_norm: str) -> bool:
"""Return whether every token in a normalized phrase is a common word.
Args:
phrase_norm (str): Normalized phrase text to inspect.
Returns:
bool: True when the phrase is non-empty and every token is a common word.
"""
tokens_ = phrase_norm.split()
common_words = get_most_common_words()
return bool(tokens_) and all(token in common_words for token in tokens_)
def score_candidate(candidate: PhraseCandidate, config: EbookSearchConfig) -> float:
"""Score a phrase candidate before LLM judging.
Args:
candidate (PhraseCandidate): Candidate to score.
config (EbookSearchConfig): Runtime phrase-tuning settings.
Returns:
float: Combined score from sources, frequency, and length, less any penalties.
"""
score = source_score(candidate) + frequency_score(candidate, config) + token_count_score(candidate, config)
if candidate.phrase_norm in get_ignored_phrases():
score -= 100.0
if has_bad_start(candidate.phrase_norm):
score -= BAD_START_SCORE_PENALTY
if has_bad_end(candidate.phrase_norm):
score -= BAD_END_SCORE_PENALTY
return score
def has_bad_start(phrase_norm: str) -> bool:
"""Return whether a normalized phrase starts with a bad starting token.
Args:
phrase_norm (str): Normalized phrase text to inspect.
Returns:
bool: True when the first token is a known bad starting token.
"""
tokens_ = phrase_norm.split()
return bool(tokens_ and tokens_[0] in get_bad_starts())
def has_bad_end(phrase_norm: str) -> bool:
"""Return whether a normalized phrase ends with a bad ending token.
Args:
phrase_norm (str): Normalized phrase text to inspect.
Returns:
bool: True when the last token is a known bad ending token.
"""
tokens_ = phrase_norm.split()
return bool(tokens_ and tokens_[-1] in get_bad_ends())
def source_score(candidate: PhraseCandidate) -> float:
"""Return the score contribution from extraction sources.
Args:
candidate (PhraseCandidate): Candidate whose enabled sources are weighted.
Returns:
float: Summed weight of the candidate's enabled extraction sources.
"""
return sum(
weight
for enabled, weight in (
(candidate.source_yake, 2.0),
(candidate.source_spacy_ner, 2.5),
(candidate.source_spacy_noun_chunk, 1.5),
(candidate.source_capitalized, 2.0),
(candidate.source_raw_ngram, 0.5),
)
if enabled
)
def frequency_score(candidate: PhraseCandidate, config: EbookSearchConfig) -> float:
"""Return the score contribution from frequency and chapter spread.
Args:
candidate (PhraseCandidate): Candidate whose counts are scored.
config (EbookSearchConfig): Runtime phrase-tuning settings holding score thresholds.
Returns:
float: Summed weight for each frequency and chapter-spread threshold the candidate meets.
"""
return sum(
weight
for count, threshold, weight in (
(candidate.raw_count, config.phrase_raw_count_score_threshold, 1.0),
(candidate.raw_count, config.phrase_raw_count_high_score_threshold, 1.0),
(candidate.chapter_count, config.phrase_chapter_count_score_threshold, 1.0),
(candidate.chapter_count, config.phrase_chapter_count_high_score_threshold, 1.0),
)
if count >= threshold
)
def token_count_score(candidate: PhraseCandidate, config: EbookSearchConfig) -> float:
"""Return the score contribution from phrase length.
Args:
candidate (PhraseCandidate): Candidate whose token count is scored.
config (EbookSearchConfig): Runtime phrase-tuning settings holding the max token bound.
Returns:
float: Length-based score contribution, which may be negative for over- or under-length phrases.
"""
if candidate.token_count == 1:
return -0.5
if candidate.token_count in {2, 3, 4}:
return 0.5
if candidate.token_count > config.phrase_max_tokens:
return -1.0
return 0.0
def get_sample_contexts(normalized_book_text: str, phrase_norm: str, max_contexts: int = 5) -> list[str]:
"""Return normalized context snippets containing a candidate phrase.
``normalized_book_text`` is expected to already be ``normalize_text``-ed by the caller
so the whole book is not re-normalized for every phrase.
Args:
normalized_book_text (str): Whole book text, already normalized, to search.
phrase_norm (str): Normalized phrase to find contexts around.
max_contexts (int): Maximum number of context snippets to return.
Returns:
list[str]: Up to ``max_contexts`` normalized snippets surrounding the phrase.
"""
contexts: list[str] = []
start = 0
while len(contexts) < max_contexts:
index = normalized_book_text.find(phrase_norm, start)
if index == -1:
break
left = max(0, index - 300)
right = min(len(normalized_book_text), index + len(phrase_norm) + 300)
contexts.append(normalized_book_text[left:right])
start = index + len(phrase_norm)
return contexts
def candidate_source_names(candidate: PhraseCandidate) -> list[str]:
"""Return enabled source names for an extracted candidate.
Args:
candidate (PhraseCandidate): Candidate whose enabled sources are listed.
Returns:
list[str]: Names of the extraction sources that produced the candidate.
"""
names: list[str] = []
if candidate.source_raw_ngram:
names.append("raw_ngram")
if candidate.source_yake:
names.append("yake")
if candidate.source_spacy_ner:
names.append("spacy_ner")
if candidate.source_spacy_noun_chunk:
names.append("spacy_noun_chunk")
if candidate.source_capitalized:
names.append("capitalized")
if candidate.source_metadata:
names.append("metadata")
return names
def extract_phrase_candidates_for_book(
book_text: str,
chapters: Sequence[str],
config: EbookSearchConfig,
*,
nlp: SpacyLanguage | None = None,
metadata: Mapping[str, object] | None = None,
) -> list[PhraseCandidate]:
"""Extract, score, and limit phrase candidates for one book.
Args:
book_text (str): Full book text used for most extraction sources.
chapters (Sequence[str]): Chapter-like text blocks used for spaCy and frequency counts.
config (EbookSearchConfig): Runtime phrase-tuning settings.
nlp (SpacyLanguage | None): Optional spaCy pipeline for entity and noun-chunk sources.
metadata (Mapping[str, object] | None): Optional book metadata used as a candidate source.
Returns:
list[PhraseCandidate]: Scored candidates sorted best-first and capped per book.
"""
started_at = perf_counter()
logger.info(
"ebook_phrase_candidate_extract_start chapters=%s chars=%s min_tokens=%s max_tokens=%s max_candidates=%s",
len(chapters),
len(book_text),
config.phrase_min_tokens,
config.phrase_max_tokens,
config.protected_phrase_max_candidates_per_book,
)
raw_started_at = perf_counter()
raw = extract_raw_ngrams(book_text, config)
logger.info(
"ebook_phrase_candidate_extract_raw_complete candidates=%s duration_ms=%.1f",
len(raw),
(perf_counter() - raw_started_at) * 1000,
)
yake_started_at = perf_counter()
yake_candidates = extract_yake_candidates(book_text, config)
logger.info(
"ebook_phrase_candidate_extract_yake_complete candidates=%s duration_ms=%.1f",
len(yake_candidates),
(perf_counter() - yake_started_at) * 1000,
)
spacy_candidates: dict[str, PhraseCandidate] = {}
if nlp is not None:
spacy_started_at = perf_counter()
for chapter in chapters:
spacy_candidates = merge_candidate_sources(spacy_candidates, extract_spacy_candidates(chapter, nlp, config))
logger.info(
"ebook_phrase_candidate_extract_spacy_complete candidates=%s duration_ms=%.1f",
len(spacy_candidates),
(perf_counter() - spacy_started_at) * 1000,
)
capitalized_started_at = perf_counter()
capitalized = extract_capitalized_phrases(book_text, config)
logger.info(
"ebook_phrase_candidate_extract_capitalized_complete candidates=%s duration_ms=%.1f",
len(capitalized),
(perf_counter() - capitalized_started_at) * 1000,
)
metadata_candidates = extract_metadata_candidates(metadata, config)
candidates = merge_candidate_sources(raw, yake_candidates, spacy_candidates, capitalized, metadata_candidates)
enriched_started_at = perf_counter()
candidates = enrich_with_frequency_and_chapter_counts(candidates, chapters)
pre_filter_count = len(candidates)
candidates, filtered_too_short, filtered_too_rare, filtered_too_common = filter_storable_candidates(
candidates,
config,
)
for candidate in candidates.values():
candidate.candidate_score = score_candidate(candidate, config)
limited = sorted(candidates.values(), key=lambda item: item.candidate_score, reverse=True)[
: config.protected_phrase_max_candidates_per_book
]
logger.info(
"ebook_phrase_candidate_extract_complete raw=%s yake=%s spacy=%s capitalized=%s metadata=%s "
"merged=%s filtered_too_short=%s filtered_too_rare=%s filtered_too_common=%s min_uses=%s "
"storable=%s limited=%s enrich_score_ms=%.1f duration_ms=%.1f",
len(raw),
len(yake_candidates),
len(spacy_candidates),
len(capitalized),
len(metadata_candidates),
pre_filter_count,
filtered_too_short,
filtered_too_rare,
filtered_too_common,
minimum_candidate_raw_count(config),
len(candidates),
len(limited),
(perf_counter() - enriched_started_at) * 1000,
(perf_counter() - started_at) * 1000,
)
return limited