Source code for langchain_community.document_loaders.web_base

"""Web base loader class."""
import asyncio
import logging
import warnings
from typing import Any, Dict, Iterator, List, Optional, Sequence, Union

import aiohttp
import requests
from langchain_core.documents import Document

from langchain_community.document_loaders.base import BaseLoader

logger = logging.getLogger(__name__)

default_header_template = {
    "User-Agent": "",
    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*"
    ";q=0.8",
    "Accept-Language": "en-US,en;q=0.5",
    "Referer": "https://www.google.com/",
    "DNT": "1",
    "Connection": "keep-alive",
    "Upgrade-Insecure-Requests": "1",
}


def _build_metadata(soup: Any, url: str) -> dict:
    """Build metadata from BeautifulSoup output."""
    metadata = {"source": url}
    if title := soup.find("title"):
        metadata["title"] = title.get_text()
    if description := soup.find("meta", attrs={"name": "description"}):
        metadata["description"] = description.get("content", "No description found.")
    if html := soup.find("html"):
        metadata["language"] = html.get("lang", "No language found.")
    return metadata


[docs]class WebBaseLoader(BaseLoader): """Load HTML pages using `urllib` and parse them with `BeautifulSoup'."""
[docs] def __init__( self, web_path: Union[str, Sequence[str]] = "", header_template: Optional[dict] = None, verify_ssl: bool = True, proxies: Optional[dict] = None, continue_on_failure: bool = False, autoset_encoding: bool = True, encoding: Optional[str] = None, web_paths: Sequence[str] = (), requests_per_second: int = 2, default_parser: str = "html.parser", requests_kwargs: Optional[Dict[str, Any]] = None, raise_for_status: bool = False, bs_get_text_kwargs: Optional[Dict[str, Any]] = None, bs_kwargs: Optional[Dict[str, Any]] = None, session: Any = None, ) -> None: """Initialize loader. Args: web_paths: Web paths to load from. requests_per_second: Max number of concurrent requests to make. default_parser: Default parser to use for BeautifulSoup. requests_kwargs: kwargs for requests raise_for_status: Raise an exception if http status code denotes an error. bs_get_text_kwargs: kwargs for beatifulsoup4 get_text bs_kwargs: kwargs for beatifulsoup4 web page parsing """ # web_path kept for backwards-compatibility. if web_path and web_paths: raise ValueError( "Received web_path and web_paths. Only one can be specified. " "web_path is deprecated, web_paths should be used." ) if web_paths: self.web_paths = list(web_paths) elif isinstance(web_path, str): self.web_paths = [web_path] elif isinstance(web_path, Sequence): self.web_paths = list(web_path) else: raise TypeError( f"web_path must be str or Sequence[str] got ({type(web_path)}) or" f" web_paths must be Sequence[str] got ({type(web_paths)})" ) self.requests_per_second = requests_per_second self.default_parser = default_parser self.requests_kwargs = requests_kwargs or {} self.raise_for_status = raise_for_status self.bs_get_text_kwargs = bs_get_text_kwargs or {} self.bs_kwargs = bs_kwargs or {} if session: self.session = session else: session = requests.Session() header_template = header_template or default_header_template.copy() if not header_template.get("User-Agent"): try: from fake_useragent import UserAgent header_template["User-Agent"] = UserAgent().random except ImportError: logger.info( "fake_useragent not found, using default user agent." "To get a realistic header for requests, " "`pip install fake_useragent`." ) session.headers = dict(header_template) session.verify = verify_ssl if proxies: session.proxies.update(proxies) self.session = session self.continue_on_failure = continue_on_failure self.autoset_encoding = autoset_encoding self.encoding = encoding
@property def web_path(self) -> str: if len(self.web_paths) > 1: raise ValueError("Multiple webpaths found.") return self.web_paths[0] async def _fetch( self, url: str, retries: int = 3, cooldown: int = 2, backoff: float = 1.5 ) -> str: async with aiohttp.ClientSession() as session: for i in range(retries): try: async with session.get( url, headers=self.session.headers, ssl=None if self.session.verify else False, cookies=self.session.cookies.get_dict(), ) as response: return await response.text() except aiohttp.ClientConnectionError as e: if i == retries - 1: raise else: logger.warning( f"Error fetching {url} with attempt " f"{i + 1}/{retries}: {e}. Retrying..." ) await asyncio.sleep(cooldown * backoff**i) raise ValueError("retry count exceeded") async def _fetch_with_rate_limit( self, url: str, semaphore: asyncio.Semaphore ) -> str: async with semaphore: try: return await self._fetch(url) except Exception as e: if self.continue_on_failure: logger.warning( f"Error fetching {url}, skipping due to" f" continue_on_failure=True" ) return "" logger.exception( f"Error fetching {url} and aborting, use continue_on_failure=True " "to continue loading urls after encountering an error." ) raise e
[docs] async def fetch_all(self, urls: List[str]) -> Any: """Fetch all urls concurrently with rate limiting.""" semaphore = asyncio.Semaphore(self.requests_per_second) tasks = [] for url in urls: task = asyncio.ensure_future(self._fetch_with_rate_limit(url, semaphore)) tasks.append(task) try: from tqdm.asyncio import tqdm_asyncio return await tqdm_asyncio.gather( *tasks, desc="Fetching pages", ascii=True, mininterval=1 ) except ImportError: warnings.warn("For better logging of progress, `pip install tqdm`") return await asyncio.gather(*tasks)
@staticmethod def _check_parser(parser: str) -> None: """Check that parser is valid for bs4.""" valid_parsers = ["html.parser", "lxml", "xml", "lxml-xml", "html5lib"] if parser not in valid_parsers: raise ValueError( "`parser` must be one of " + ", ".join(valid_parsers) + "." )
[docs] def scrape_all(self, urls: List[str], parser: Union[str, None] = None) -> List[Any]: """Fetch all urls, then return soups for all results.""" from bs4 import BeautifulSoup results = asyncio.run(self.fetch_all(urls)) final_results = [] for i, result in enumerate(results): url = urls[i] if parser is None: if url.endswith(".xml"): parser = "xml" else: parser = self.default_parser self._check_parser(parser) final_results.append(BeautifulSoup(result, parser, **self.bs_kwargs)) return final_results
def _scrape( self, url: str, parser: Union[str, None] = None, bs_kwargs: Optional[dict] = None, ) -> Any: from bs4 import BeautifulSoup if parser is None: if url.endswith(".xml"): parser = "xml" else: parser = self.default_parser self._check_parser(parser) html_doc = self.session.get(url, **self.requests_kwargs) if self.raise_for_status: html_doc.raise_for_status() if self.encoding is not None: html_doc.encoding = self.encoding elif self.autoset_encoding: html_doc.encoding = html_doc.apparent_encoding return BeautifulSoup(html_doc.text, parser, **(bs_kwargs or {}))
[docs] def scrape(self, parser: Union[str, None] = None) -> Any: """Scrape data from webpage and return it in BeautifulSoup format.""" if parser is None: parser = self.default_parser return self._scrape(self.web_path, parser=parser, bs_kwargs=self.bs_kwargs)
[docs] def lazy_load(self) -> Iterator[Document]: """Lazy load text from the url(s) in web_path.""" for path in self.web_paths: soup = self._scrape(path, bs_kwargs=self.bs_kwargs) text = soup.get_text(**self.bs_get_text_kwargs) metadata = _build_metadata(soup, path) yield Document(page_content=text, metadata=metadata)
[docs] def aload(self) -> List[Document]: # type: ignore """Load text from the urls in web_path async into Documents.""" results = self.scrape_all(self.web_paths) docs = [] for path, soup in zip(self.web_paths, results): text = soup.get_text(**self.bs_get_text_kwargs) metadata = _build_metadata(soup, path) docs.append(Document(page_content=text, metadata=metadata)) return docs