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import logging
import re
from pathlib import Path
from typing import Any, Iterator, List, Mapping, Optional
from langchain_core.documents import Document
from langchain_community.document_loaders.base import BaseLoader
from langchain_community.utilities.bibtex import BibtexparserWrapper
logger = logging.getLogger(__name__)
class BibtexLoader(BaseLoader):
"""Load a `bibtex` file.
Each document represents one entry from the bibtex file.
If a PDF file is present in the `file` bibtex field, the original PDF
is loaded into the document text. If no such file entry is present,
the `abstract` field is used instead.
"""
def __init__(
self,
file_path: str,
*,
parser: Optional[BibtexparserWrapper] = None,
max_docs: Optional[int] = None,
max_content_chars: Optional[int] = 4_000,
load_extra_metadata: bool = False,
file_pattern: str = r"[^:]+\.pdf",
):
"""Initialize the BibtexLoader.
Args:
file_path: Path to the bibtex file.
parser: The parser to use. If None, a default parser is used.
max_docs: Max number of associated documents to load. Use -1 means
no limit.
max_content_chars: Maximum number of characters to load from the PDF.
load_extra_metadata: Whether to load extra metadata from the PDF.
file_pattern: Regex pattern to match the file name in the bibtex.
"""
self.file_path = file_path
self.parser = parser or BibtexparserWrapper()
self.max_docs = max_docs
self.max_content_chars = max_content_chars
self.load_extra_metadata = load_extra_metadata
self.file_regex = re.compile(file_pattern)
def _load_entry(self, entry: Mapping[str, Any]) -> Optional[Document]:
import fitz
parent_dir = Path(self.file_path).parent
# regex is useful for Zotero flavor bibtex files
file_names = self.file_regex.findall(entry.get("file", ""))
if not file_names:
return None
texts: List[str] = []
for file_name in file_names:
try:
with fitz.open(parent_dir / file_name) as f:
texts.extend(page.get_text() for page in f)
except FileNotFoundError as e:
logger.debug(e)
content = "\n".join(texts) or entry.get("abstract", "")
if self.max_content_chars:
content = content[: self.max_content_chars]
metadata = self.parser.get_metadata(entry, load_extra=self.load_extra_metadata)
return Document(
page_content=content,
metadata=metadata,
)
def lazy_load(self) -> Iterator[Document]:
"""Load bibtex file using bibtexparser and get the article texts plus the
article metadata.
See https://bibtexparser.readthedocs.io/en/master/
Returns:
a list of documents with the document.page_content in text format
"""
try:
import fitz # noqa: F401
except ImportError:
raise ImportError(
"PyMuPDF package not found, please install it with "
"`pip install pymupdf`"
)
entries = self.parser.load_bibtex_entries(self.file_path)
if self.max_docs:
entries = entries[: self.max_docs]
for entry in entries:
doc = self._load_entry(entry)
if doc:
yield doc
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