# Source: https://trigger.dev/docs/guides/python/python-crawl4ai.md

> ## Documentation Index
> Fetch the complete documentation index at: https://trigger.dev/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Python headless browser web crawler example

> Learn how to use Python, Crawl4AI and Playwright to create a headless browser web crawler with Trigger.dev.

## Overview

This demo showcases how to use Trigger.dev with Python to build a web crawler that uses a headless browser to navigate websites and extract content.

## Prerequisites

* A project with [Trigger.dev initialized](/quick-start)
* [Python](https://www.python.org/) installed on your local machine

## Features

* [Trigger.dev](https://trigger.dev) for background task orchestration
* Our [Python build extension](/config/extensions/pythonExtension) to install the dependencies and run the Python script
* [Crawl4AI](https://github.com/unclecode/crawl4ai), an open source LLM friendly web crawler
* A custom [Playwright extension](https://playwright.dev/) to create a headless chromium browser
* Proxy support

## Using Proxies

<Warning>
  **WEB SCRAPING:** When web scraping, you MUST use a proxy to comply with our terms of service. Direct scraping of third-party websites without the site owner's permission using Trigger.dev Cloud is prohibited and will result in account suspension. See [this example](/guides/examples/puppeteer#scrape-content-from-a-web-page) which uses a proxy.
</Warning>

Some popular proxy services are:

* [Smartproxy](https://smartproxy.com/)
* [Bright Data](https://brightdata.com/)
* [Browserbase](https://browserbase.com/)
* [Oxylabs](https://oxylabs.io/)
* [ScrapingBee](https://scrapingbee.com/)

Once you have a proxy service, set the following environment variables in your Trigger.dev .env file, and add them in the Trigger.dev dashboard:

* `PROXY_URL`: The URL of your proxy server (e.g., `http://proxy.example.com:8080`)
* `PROXY_USERNAME`: Username for authenticated proxies (optional)
* `PROXY_PASSWORD`: Password for authenticated proxies (optional)

## GitHub repo

<Card title="View the project on GitHub" icon="GitHub" href="https://github.com/triggerdotdev/examples/tree/main/python-crawl4ai">
  Click here to view the full code for this project in our examples repository on GitHub. You can
  fork it and use it as a starting point for your own project.
</Card>

## The code

### Build configuration

After you've initialized your project with Trigger.dev, add these build settings to your `trigger.config.ts` file:

```ts trigger.config.ts theme={"theme":"css-variables"}
import { defineConfig } from "@trigger.dev/sdk";
import { pythonExtension } from "@trigger.dev/python/extension";
import type { BuildContext, BuildExtension } from "@trigger.dev/core/build";

export default defineConfig({
  project: "<project ref>",
  // Your other config settings...
  build: {
    extensions: [
      // This is required to use the Python extension
      pythonExtension(),
      // This is required to create a headless chromium browser with Playwright
      installPlaywrightChromium(),
    ],
  },
});

// This is a custom build extension to install Playwright and Chromium
export function installPlaywrightChromium(): BuildExtension {
  return {
    name: "InstallPlaywrightChromium",
    onBuildComplete(context: BuildContext) {
      const instructions = [
        // Base and Chromium dependencies
        `RUN apt-get update && apt-get install -y --no-install-recommends \
          curl unzip npm libnspr4 libatk1.0-0 libatk-bridge2.0-0 libatspi2.0-0 \
          libasound2 libnss3 libxcomposite1 libxdamage1 libxfixes3 libxrandr2 \
          libgbm1 libxkbcommon0 \
          && apt-get clean && rm -rf /var/lib/apt/lists/*`,

        // Install Playwright and Chromium
        `RUN npm install -g playwright`,
        `RUN mkdir -p /ms-playwright`,
        `RUN PLAYWRIGHT_BROWSERS_PATH=/ms-playwright python -m playwright install --with-deps chromium`,
      ];

      context.addLayer({
        id: "playwright",
        image: { instructions },
        deploy: {
          env: {
            PLAYWRIGHT_BROWSERS_PATH: "/ms-playwright",
            PLAYWRIGHT_SKIP_BROWSER_DOWNLOAD: "1",
            PLAYWRIGHT_SKIP_BROWSER_VALIDATION: "1",
          },
          override: true,
        },
      });
    },
  };
}
```

<Info>
  Learn more about executing scripts in your Trigger.dev project using our Python build extension
  [here](/config/extensions/pythonExtension).
</Info>

### Task code

This task uses the `python.runScript` method to run the `crawl-url.py` script with the given URL as an argument. You can see the original task in our examples repository [here](https://github.com/triggerdotdev/examples/blob/main/python-crawl4ai/src/trigger/pythonTasks.ts).

```ts src/trigger/pythonTasks.ts theme={"theme":"css-variables"}
import { logger, schemaTask, task } from "@trigger.dev/sdk";
import { python } from "@trigger.dev/python";
import { z } from "zod";

export const convertUrlToMarkdown = schemaTask({
  id: "convert-url-to-markdown",
  schema: z.object({
    url: z.string().url(),
  }),
  run: async (payload) => {
    // Pass through any proxy environment variables
    const env = {
      PROXY_URL: process.env.PROXY_URL,
      PROXY_USERNAME: process.env.PROXY_USERNAME,
      PROXY_PASSWORD: process.env.PROXY_PASSWORD,
    };

    const result = await python.runScript("./src/python/crawl-url.py", [payload.url], { env });

    logger.debug("convert-url-to-markdown", {
      url: payload.url,
      result,
    });

    return result.stdout;
  },
});
```

### Add a requirements.txt file

Add the following to your `requirements.txt` file. This is required in Python projects to install the dependencies.

```txt requirements.txt theme={"theme":"css-variables"}
crawl4ai
playwright
urllib3<2.0.0
```

### The Python script

The Python script is a simple script using Crawl4AI that takes a URL and returns the markdown content of the page. You can see the original script in our examples repository [here](https://github.com/triggerdotdev/examples/blob/main/python-crawl4ai/src/python/crawl-url.py).

```python src/python/crawl-url.py theme={"theme":"css-variables"}
import asyncio
import sys
import os
from crawl4ai import *
from crawl4ai.async_configs import BrowserConfig

async def main(url: str):
    # Get proxy configuration from environment variables
    proxy_url = os.environ.get("PROXY_URL")
    proxy_username = os.environ.get("PROXY_USERNAME")
    proxy_password = os.environ.get("PROXY_PASSWORD")

    # Configure the proxy
    browser_config = None
    if proxy_url:
        if proxy_username and proxy_password:
            # Use authenticated proxy
            proxy_config = {
                "server": proxy_url,
                "username": proxy_username,
                "password": proxy_password
            }
            browser_config = BrowserConfig(proxy_config=proxy_config)
        else:
            # Use simple proxy
            browser_config = BrowserConfig(proxy=proxy_url)
    else:
        browser_config = BrowserConfig()

    async with AsyncWebCrawler(config=browser_config) as crawler:
        result = await crawler.arun(
            url=url,
        )
        print(result.markdown)

if __name__ == "__main__":
    if len(sys.argv) < 2:
        print("Usage: python crawl-url.py <url>")
        sys.exit(1)
    url = sys.argv[1]
    asyncio.run(main(url))
```

## Testing your task

1. Create a virtual environment `python -m venv venv`
2. Activate the virtual environment, depending on your OS: On Mac/Linux: `source venv/bin/activate`, on Windows: `venv\Scripts\activate`
3. Install the Python dependencies `pip install -r requirements.txt`
4. If you haven't already, copy your project ref from your [Trigger.dev dashboard](https://cloud.trigger.dev) and add it to the `trigger.config.ts` file.
5. Run the Trigger.dev CLI `dev` command (it may ask you to authorize the CLI if you haven't already).
6. Test the task in the dashboard, using a URL of your choice.

<Warning>
  **WEB SCRAPING:** When web scraping, you MUST use a proxy to comply with our terms of service. Direct scraping of third-party websites without the site owner's permission using Trigger.dev Cloud is prohibited and will result in account suspension. See [this example](/guides/examples/puppeteer#scrape-content-from-a-web-page) which uses a proxy.
</Warning>

## Deploying your task

Deploy the task to production using the Trigger.dev CLI `deploy` command.

## Learn more about using Python with Trigger.dev

<Card title="Python build extension" icon="code" href="/config/extensions/pythonExtension">
  Learn how to use our built-in Python build extension to install dependencies and run your Python
  code.
</Card>