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🌐 CSS Scraper Provider (css_scraper)

The CSS Scraper is a versatile provider that can extract a price from any public webpage using a CSS selector. It is one of the Asset Providers — it does not rely on a specific financial data API.

📖 User Guide: CSS Scraper — User Manual

⚙️ How it Works

  1. Configuration: When assigning this provider to an asset, you must provide:

    • identifier: The URL of the webpage to scrape.
    • identifier_type: URL
    • provider_params:
      • current_css_selector (required): The CSS selector to locate the price element on the page (e.g., #sp-last, .price-value).
      • currency (required): The currency of the price (ISO 4217).
      • decimal_format (optional): us (e.g., 1,234.56) or eu (e.g., 1.234,56). Default: us.
      • timeout (optional): HTTP request timeout in seconds. Default: 30.
      • user_agent (optional): Custom User-Agent header. Default: LibreFolio/1.0.

  2. Execution:

    • Fetches the HTML of the specified URL via httpx (async HTTP client).
    • Uses BeautifulSoup to parse the HTML and find the element matching the CSS selector.
    • Extracts the text content and parses it into a Decimal value, handling different number formats based on decimal_format.

  3. get_asset_url(): Returns the identifier URL itself (the page being scraped).

  4. params_schema: Exposes all 5 configuration fields for dynamic form generation in the frontend.

🔢 Decimal Format Remapping

The decimal_format parameter controls how the scraped text is parsed into a number:

Format Input Example Parsed Value
us (default) 1,234.56 1234.56
eu 1.234,56 1234.56

The parser strips all non-numeric characters except the decimal separator, then converts to Decimal. Group separators (, for US, . for EU) are removed first.

⚡ Caching & Performance

  • No response caching: Each get_current_value() call performs a fresh HTTP request. This is intentional — scraped data may change frequently and the provider cannot predict staleness.
  • Connection pooling: Uses httpx.AsyncClient with connection reuse across requests.
  • Timeout handling: Configurable per-asset via timeout parameter. Default 30s prevents blocking on slow sites.

📋 Use Cases

  • Tracking the price of an asset from a financial news website.
  • Scraping data from a niche market data provider that doesn't have an API.
  • Tracking the value of a collectible from an auction site.

⚠️ Limitations

  • No Historical Data: supports_history = False. It can only fetch the current value.
  • Fragile: If the website's layout changes, the CSS selector may break. Use the probe endpoint to test before saving.
  • Requires Public Access: It cannot access pages that require a login.
  • Rate limits: No built-in rate limiting. High-frequency sync may trigger the target site's anti-bot protection.