web-scraping

# Web scraping methodology

Patterns for reliable, ethical web scraping with fallback strategies and anti-bot handling.

## Scraping cascade architecture

Implement multiple extraction strategies with automatic fallback:

```python
from abc import ABC, abstractmethod
from typing import Optional
import requests
from bs4 import BeautifulSoup
import trafilatura

#for .py files
from playwright.sync_api import sync_playwright
from playwright_stealth import stealth_sync

#for .ipynb files
import asyncio
from playwright.async_api import async_playwright

class ScrapingResult:
    def __init__(self, content: str, title: str, method: str):
        self.content = content
        self.title = title
        self.method = method  # Track which method succeeded

class Scraper(ABC):
    @abstractmethod
    def fetch(self, url: str) -> Optional[ScrapingResult]: ...

class TrafilaturaCscraper(Scraper):
    """Fast, lightweight extraction for standard articles."""

    def fetch(self, url: str) -> Optional[ScrapingResult]:
        try:
            downloaded = trafilatura.fetch_url(url)
            if not downloaded:
                return None

            content = trafilatura.extract(
                downloaded,
                include_comments=False,
                include_tables=True,
                favor_recall=True
            )

            if not content or len(content) < 100:
                return None

            # Extract title separately
            soup = BeautifulSoup(downloaded, 'html.parser')
            title = soup.find('title')
            title_text = title.get_text() if title else ''

            return ScrapingResult(content, title_text, 'trafilatura')
        except Exception:
            return None

class RequestsScraper(Scraper):
    """HTTP requests with rotating user agents."""

    USER_AGENTS = [
        'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36',
        'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36',
        'Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36',
    ]

    def fetch(self, url: str) -> Optional[ScrapingResult]:
        import random

        headers = {
            'User-Agent': random.choice(self.USER_AGENTS),
            'Accept': 'text/html,application/xhtml+xml',
            'Accept-Language': 'en-US,en;q=0.9',
        }

        try:
            response = requests.get(url, headers=headers, timeout=30)
            response.raise_for_status()

            soup = BeautifulSoup(response.text, 'html.parser')

            # Remove script/style elements
            for element in soup(['script', 'style', 'nav', 'footer', 'aside']):
                element.decompose()

            # Find main content
            main = soup.find('main') or soup.find('article') or soup.find('body')
            content = main.get_text(separator='\n', strip=True) if main else ''

            title = soup.find('title')
            title_text = title.get_text() if title else ''

            if len(content) < 100:
                return None

            return ScrapingResult(content, title_text, 'requests')
        except Exception:
            return None

class PlaywrightScraper(Scraper):
    """Heavy JavaScript rendering with stealth mode for anti-bot bypass."""

    def fetch(self, url: str) -> Optional[ScrapingResult]:
        try:
            with sync_playwright() as p:
                browser = p.chromium.launch(headless=True)
                context = browser.new_context(
                    viewport={'width': 1920, 'height': 1080},
                    user_agent='Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36'
                )
                page = context.new_page()

                # Apply stealth to avoid detection
                stealth_sync(page)

                page.goto(url, wait_until='networkidle', timeout=60000)

                # Wait for content to load
                page.wait_for_timeout(2000)

                # Extract content
                content = page.evaluate('''() => {
                    const article = document.querySelector('article, main, .content, #content');
                    return article ? article.innerText : document.body.innerText;
                }''')

                title = page.title()

                browser.close()

                if len(content) < 100:
                    return None

                return ScrapingResult(content, title, 'playwright')
        except Exception:
            return None

class PlaywrightScraperAsync:
    """Async Playwright scraper for Jupyter notebooks (.ipynb files).
    
    Jupyter notebooks run their own event loop, so sync Playwright won't work.
    Use this async version with `await` in notebook cells.
    """

    async def fetch(self, url: str) -> Optional[ScrapingResult]:
        try:
            async with async_playwright() as p:
                browser = await p.chromium.launch(headless=True)
                context = await browser.new_context(
                    viewport={'width': 1920, 'height': 1080},
                    user_agent='Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36'
                )
                page = await context.new_page()

                # Note: playwright-stealth async version
                # from playwright_stealth import stealth_async
                # await stealth_async(page)

                await page.goto(url, wait_until='networkidle', timeout=60000)

                # Wait for content to load
                await page.wait_for_timeout(2000)

                # Extract content
                content = await page.evaluate('''() => {
                    const article = document.querySelector('article, main, .content, #content');
                    return article ? article.innerText : document.body.innerText;
                }''')

                title = await page.title()

                await browser.close()

                if len(content) < 100: