Loading Javascript from a string in Python with aiohttp

In this guide, we'll show you how to load custom javascript code as a given string when converting an HTML document to PDF using PDFShift's API. This allows you to add custom JS to your page to customize the output of your generated PDF.

It can be interesting to be able to set a custom JS value to adjust the rendering of your page specifically when exporting the document to PDF. This allows you to keep a standard look and feel to your users, but adjust some areas when sending that same document to PDFShift to get back a PDF.

import aiohttp, asyncio, json, base64

# You can get an API key at https://pdfshift.io
api_key = 'sk_xxxxxxxxxxxx'

params = {
    'source': 'https://www.example.com',
    'javascript': 'document.querySelector("h1").style.color = "red";'
}

response = None
try:
    auth = base64.b64encode(
        'api:{}'.format(api_key).encode('utf-8')
    ).decode('utf-8')

    async with aiohttp.ClientSession() as session:
        async with session.post(
            'https://api.pdfshift.io/v3/convert/pdf',
            headers={'Authorization': f'Basic {auth}'},
            json=params
        ) as response:
            if response.status >= 400:
                raise Exception('Invalid request: {}'.format(await response.text()))

            with open('result.pdf', 'wb') as f:
                f.write(await response.read())

            print('The PDF document was generated and saved to result.pdf')
except asyncio.TimeoutError:
    raise Exception('The request took too long to process')
except aiohttp.ClientError as e:
    raise Exception(f'An error occurred: {e}')
except Exception as e:
    # We highly recommend you to handle exceptions. Often, PDFShift will provide you with a clear explanation about what happened.
    # Moreover, in case of error, no PDF are returned !
    raise Exception(f'An error occurred: {e}')

The javascript parameter accepts either a string or a URL. It will be used as the javascript for the page when converting it to PDF. This allows you to set a custom JS value to adjust the rendering of your page specifically when exporting the document to PDF.

For further details on the javascript property and its usage, please refer to our dedicated documentation.

We hope this guide was helpful. If you have any questions or noticed any issues on the code above,
feel free to drop us a line.