mirror of
https://github.com/hwchase17/langchain
synced 2024-11-02 09:40:22 +00:00
265 lines
9.9 KiB
Python
265 lines
9.9 KiB
Python
"""Web base loader class."""
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import asyncio
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import logging
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import warnings
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from typing import Any, Dict, Iterator, List, Optional, Sequence, Union
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import aiohttp
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import requests
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from langchain_core.documents import Document
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from langchain_community.document_loaders.base import BaseLoader
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logger = logging.getLogger(__name__)
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default_header_template = {
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"User-Agent": "",
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"Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*"
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";q=0.8",
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"Accept-Language": "en-US,en;q=0.5",
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"Referer": "https://www.google.com/",
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"DNT": "1",
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"Connection": "keep-alive",
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"Upgrade-Insecure-Requests": "1",
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}
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def _build_metadata(soup: Any, url: str) -> dict:
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"""Build metadata from BeautifulSoup output."""
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metadata = {"source": url}
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if title := soup.find("title"):
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metadata["title"] = title.get_text()
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if description := soup.find("meta", attrs={"name": "description"}):
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metadata["description"] = description.get("content", "No description found.")
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if html := soup.find("html"):
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metadata["language"] = html.get("lang", "No language found.")
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return metadata
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class WebBaseLoader(BaseLoader):
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"""Load HTML pages using `urllib` and parse them with `BeautifulSoup'."""
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def __init__(
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self,
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web_path: Union[str, Sequence[str]] = "",
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header_template: Optional[dict] = None,
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verify_ssl: bool = True,
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proxies: Optional[dict] = None,
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continue_on_failure: bool = False,
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autoset_encoding: bool = True,
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encoding: Optional[str] = None,
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web_paths: Sequence[str] = (),
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requests_per_second: int = 2,
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default_parser: str = "html.parser",
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requests_kwargs: Optional[Dict[str, Any]] = None,
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raise_for_status: bool = False,
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bs_get_text_kwargs: Optional[Dict[str, Any]] = None,
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bs_kwargs: Optional[Dict[str, Any]] = None,
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session: Any = None,
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) -> None:
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"""Initialize loader.
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Args:
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web_paths: Web paths to load from.
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requests_per_second: Max number of concurrent requests to make.
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default_parser: Default parser to use for BeautifulSoup.
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requests_kwargs: kwargs for requests
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raise_for_status: Raise an exception if http status code denotes an error.
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bs_get_text_kwargs: kwargs for beatifulsoup4 get_text
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bs_kwargs: kwargs for beatifulsoup4 web page parsing
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"""
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# web_path kept for backwards-compatibility.
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if web_path and web_paths:
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raise ValueError(
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"Received web_path and web_paths. Only one can be specified. "
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"web_path is deprecated, web_paths should be used."
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)
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if web_paths:
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self.web_paths = list(web_paths)
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elif isinstance(web_path, str):
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self.web_paths = [web_path]
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elif isinstance(web_path, Sequence):
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self.web_paths = list(web_path)
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else:
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raise TypeError(
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f"web_path must be str or Sequence[str] got ({type(web_path)}) or"
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f" web_paths must be Sequence[str] got ({type(web_paths)})"
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)
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self.requests_per_second = requests_per_second
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self.default_parser = default_parser
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self.requests_kwargs = requests_kwargs or {}
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self.raise_for_status = raise_for_status
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self.bs_get_text_kwargs = bs_get_text_kwargs or {}
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self.bs_kwargs = bs_kwargs or {}
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if session:
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self.session = session
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else:
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session = requests.Session()
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header_template = header_template or default_header_template.copy()
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if not header_template.get("User-Agent"):
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try:
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from fake_useragent import UserAgent
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header_template["User-Agent"] = UserAgent().random
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except ImportError:
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logger.info(
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"fake_useragent not found, using default user agent."
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"To get a realistic header for requests, "
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"`pip install fake_useragent`."
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)
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session.headers = dict(header_template)
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session.verify = verify_ssl
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if proxies:
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session.proxies.update(proxies)
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self.session = session
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self.continue_on_failure = continue_on_failure
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self.autoset_encoding = autoset_encoding
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self.encoding = encoding
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@property
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def web_path(self) -> str:
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if len(self.web_paths) > 1:
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raise ValueError("Multiple webpaths found.")
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return self.web_paths[0]
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async def _fetch(
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self, url: str, retries: int = 3, cooldown: int = 2, backoff: float = 1.5
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) -> str:
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async with aiohttp.ClientSession() as session:
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for i in range(retries):
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try:
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async with session.get(
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url,
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headers=self.session.headers,
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ssl=None if self.session.verify else False,
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cookies=self.session.cookies.get_dict(),
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) as response:
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return await response.text()
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except aiohttp.ClientConnectionError as e:
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if i == retries - 1:
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raise
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else:
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logger.warning(
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f"Error fetching {url} with attempt "
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f"{i + 1}/{retries}: {e}. Retrying..."
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)
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await asyncio.sleep(cooldown * backoff**i)
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raise ValueError("retry count exceeded")
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async def _fetch_with_rate_limit(
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self, url: str, semaphore: asyncio.Semaphore
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) -> str:
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async with semaphore:
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try:
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return await self._fetch(url)
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except Exception as e:
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if self.continue_on_failure:
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logger.warning(
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f"Error fetching {url}, skipping due to"
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f" continue_on_failure=True"
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)
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return ""
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logger.exception(
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f"Error fetching {url} and aborting, use continue_on_failure=True "
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"to continue loading urls after encountering an error."
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)
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raise e
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async def fetch_all(self, urls: List[str]) -> Any:
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"""Fetch all urls concurrently with rate limiting."""
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semaphore = asyncio.Semaphore(self.requests_per_second)
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tasks = []
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for url in urls:
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task = asyncio.ensure_future(self._fetch_with_rate_limit(url, semaphore))
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tasks.append(task)
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try:
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from tqdm.asyncio import tqdm_asyncio
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return await tqdm_asyncio.gather(
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*tasks, desc="Fetching pages", ascii=True, mininterval=1
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)
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except ImportError:
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warnings.warn("For better logging of progress, `pip install tqdm`")
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return await asyncio.gather(*tasks)
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@staticmethod
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def _check_parser(parser: str) -> None:
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"""Check that parser is valid for bs4."""
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valid_parsers = ["html.parser", "lxml", "xml", "lxml-xml", "html5lib"]
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if parser not in valid_parsers:
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raise ValueError(
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"`parser` must be one of " + ", ".join(valid_parsers) + "."
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)
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def scrape_all(self, urls: List[str], parser: Union[str, None] = None) -> List[Any]:
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"""Fetch all urls, then return soups for all results."""
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from bs4 import BeautifulSoup
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results = asyncio.run(self.fetch_all(urls))
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final_results = []
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for i, result in enumerate(results):
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url = urls[i]
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if parser is None:
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if url.endswith(".xml"):
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parser = "xml"
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else:
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parser = self.default_parser
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self._check_parser(parser)
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final_results.append(BeautifulSoup(result, parser, **self.bs_kwargs))
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return final_results
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def _scrape(
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self,
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url: str,
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parser: Union[str, None] = None,
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bs_kwargs: Optional[dict] = None,
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) -> Any:
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from bs4 import BeautifulSoup
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if parser is None:
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if url.endswith(".xml"):
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parser = "xml"
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else:
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parser = self.default_parser
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self._check_parser(parser)
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html_doc = self.session.get(url, **self.requests_kwargs)
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if self.raise_for_status:
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html_doc.raise_for_status()
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if self.encoding is not None:
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html_doc.encoding = self.encoding
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elif self.autoset_encoding:
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html_doc.encoding = html_doc.apparent_encoding
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return BeautifulSoup(html_doc.text, parser, **(bs_kwargs or {}))
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def scrape(self, parser: Union[str, None] = None) -> Any:
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"""Scrape data from webpage and return it in BeautifulSoup format."""
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if parser is None:
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parser = self.default_parser
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return self._scrape(self.web_path, parser=parser, bs_kwargs=self.bs_kwargs)
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def lazy_load(self) -> Iterator[Document]:
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"""Lazy load text from the url(s) in web_path."""
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for path in self.web_paths:
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soup = self._scrape(path, bs_kwargs=self.bs_kwargs)
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text = soup.get_text(**self.bs_get_text_kwargs)
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metadata = _build_metadata(soup, path)
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yield Document(page_content=text, metadata=metadata)
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def aload(self) -> List[Document]:
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"""Load text from the urls in web_path async into Documents."""
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results = self.scrape_all(self.web_paths)
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docs = []
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for path, soup in zip(self.web_paths, results):
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text = soup.get_text(**self.bs_get_text_kwargs)
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metadata = _build_metadata(soup, path)
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docs.append(Document(page_content=text, metadata=metadata))
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return docs
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