Tadpole – A modular and extensible DSL built for web scraping
34 points
5 hours ago
| 2 comments
| tadpolehq.com
| HN
zachperkitny
5 hours ago
[-]
Hello!

I wanted to share my recent project: Tadpole. It is a custom DSL built on top of KDL specifically for web scraping and browser automation. I wanted there to be a standardized way of writing scrapers and reusing existing scraper logic. This was my solution.

Why?

    Abstraction: Simulating realistic human behavior (bezier curves, easing) through high-level composed actions.
    Zero Config: Import and share scraper modules directly via Git, bypass NPM/Registry overhead.
    Reusability: Actions and evaluators can be composed through slots to create more complex workflows.

Example

This is a fully running example, @tadpole/cli is published on npm:

tadpole run redfin.kdl --input '{"text": "Seattle, WA"}' --auto --output output.json

  import "modules/redfin/mod.kdl" repo="github.com/tadpolehq/community"

  main {
    new_page {
      redfin.search text="=text"
      wait_until
      redfin.extract_from_card extract_to="addresses" {
        address {
          redfin.extract_address_from_card
        }
      }
    }
  }

Roadmap? Planned for 0.2.0

    Control Flow: Add maybe (effectively try/catch) and loop (while {}, do {})
    DOMPick: Used to select elements by index
    DOMFilter: Used to filter elements using evaluators
    More Evaluators: Type casting, regex, exists
    Root Slots: Support for top level dynamic placeholders
    Error Reporting: More robust error reporting
    Logging: More consistent logging from actions and add log action to global registry
0.3.0

    Piping: Allowing different files to chain input/output.
    Outputs: Complex output sinks to databases, s3, kafka, etc.
    DAGs: Use directed acylic graphs to create complex crawling scenarios and parallel compute.
Github Repository: https://github.com/tadpolehq/tadpole

I've also created a community repository for sharing scraper logic: https://github.com/tadpolehq/community

Feedback would be greatly appreciated!

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bobajeff
4 hours ago
[-]
I like the idea of a DSL for scraping but my scrapers do more than extract text. I also download files (+monitor download progress) and intercept images (+ check for partial or failed to load images). So it seems my use case isn't really covered with this.
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zachperkitny
3 hours ago
[-]
Thanks for the idea actually! It's difficult to cover every use case in the 0.1.0 release. I'll take this into account. Downloading Files/Images could likely be abstracted into just an HTTP source and the data sources could be merged in some way.
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bobajeff
4 hours ago
[-]
I had to look up what KDL is and what `Functional Source License, Version 1.1, ALv2 Future License` is.

So KDL is like another JSON or Yaml. FSL-1.1-ALv2 is an, almost but not really, open source license that after a 2 years becomes available under a real open source license. It's to prevent free loading from companies or something. Sounds fine to me actually.

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zachperkitny
3 hours ago
[-]
Effectively, it's not meant to restrict people from using it, even in a commercial setting, just to protect my personal interests in what I want to do with it in a commercial setting.

KDL is more than just JSON or YAML. It's node based. It's output in libraries is effectively an AST and its use cases are open ended.

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