"""Web base loader class."""
import asyncio
import logging
import warnings
from typing import Any, List, Optional, Union
import aiohttp
import requests
from langchain.docstore.document import Document
from langchain.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", None)
if html := soup.find("html"):
metadata["language"] = html.get("lang", None)
return metadata
[docs]class WebBaseLoader(BaseLoader):
"""Loader that uses urllib and beautiful soup to load webpages."""
web_paths: List[str]
requests_per_second: int = 2
"""Max number of concurrent requests to make."""
default_parser: str = "html.parser"
"""Default parser to use for BeautifulSoup."""
def __init__(
self, web_path: Union[str, List[str]], header_template: Optional[dict] = None
):
"""Initialize with webpage path."""
# TODO: Deprecate web_path in favor of web_paths, and remove this
# left like this because there are a number of loaders that expect single
# urls
if isinstance(web_path, str):
self.web_paths = [web_path]
elif isinstance(web_path, List):
self.web_paths = web_path
self.session = requests.Session()
try:
import bs4 # noqa:F401
except ImportError:
raise ValueError(
"bs4 package not found, please install it with " "`pip install bs4`"
)
try:
from fake_useragent import UserAgent
headers = header_template or default_header_template
headers["User-Agent"] = UserAgent().random
self.session.headers = dict(headers)
except ImportError:
logger.info(
"fake_useragent not found, using default user agent."
"To get a realistic header for requests, `pip install fake_useragent`."
)
@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
) 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:
return await self._fetch(url)
[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))
return final_results
def _scrape(self, url: str, parser: Union[str, None] = 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)
return BeautifulSoup(html_doc.text, parser)
[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)
[docs] def load(self) -> List[Document]:
"""Load text from the url(s) in web_path."""
docs = []
for path in self.web_paths:
soup = self._scrape(path)
text = soup.get_text()
metadata = _build_metadata(soup, path)
docs.append(Document(page_content=text, metadata=metadata))
return docs
[docs] def aload(self) -> List[Document]:
"""Load text from the urls in web_path async into Documents."""
results = self.scrape_all(self.web_paths)
docs = []
for i in range(len(results)):
soup = results[i]
text = soup.get_text()
metadata = _build_metadata(soup, self.web_paths[i])
docs.append(Document(page_content=text, metadata=metadata))
return docs