PDF generation

WeasyPrint ships with the pdf extra and converts HTML and CSS to PDF.

pip install "feather-framework[pdf]"

Basic usage

Build the document from a Jinja template, the same way you build a page. It escapes what people typed, so a card titled <img src=...> prints as text instead of becoming markup.

from flask import render_template
from weasyprint import CSS, HTML


def _no_fetch(url, *args, **kwargs):
    """Load inline data only. The HTML holds what users typed, so a fetcher that
    followed URLs would let them make your server request any address."""
    if url.startswith("data:"):
        from weasyprint.urls import default_url_fetcher

        return default_url_fetcher(url, *args, **kwargs)
    raise ValueError("External resources are not loaded in exports")


def report_pdf(report) -> bytes:
    html = render_template("exports/report.html", report=report)
    css = CSS(string=render_template("exports/report.css"), url_fetcher=_no_fetch)
    return HTML(string=html, url_fetcher=_no_fetch).write_pdf(stylesheets=[css])

Return it from a route as a download:

@page.get("/reports/<report_id>/export")
@auth_required
@inject(ReportService)
def export_report(report_service, report_id):
    report = report_service.get_for_user(report_id, current_user.id)
    response = make_response(report_pdf(report))
    response.headers["Content-Type"] = "application/pdf"
    response.headers["Content-Disposition"] = 'attachment; filename="report.pdf"'
    return response

Don’t build the HTML with an f-string. Nothing is escaped, and anything a user typed becomes markup in the PDF, including tags that make WeasyPrint fetch URLs.

Keep the stylesheet free of template variables too. A running footer that repeats the title takes it from the page with string-set, so nothing a user typed is ever parsed as CSS:

@page { @bottom-left { content: string(doctitle); } }
h1 { string-set: doctitle content(text); }

The Docker image Feather generates installs fonts-inter and fonts-dejavu-core. The slim base image has no fonts of its own, so without them a PDF rendered in production has no typeface for its text. Name a font the image has (font-family: "Inter", "DejaVu Sans", sans-serif) or bundle your own.

Saving to storage

from feather.storage import get_storage

@api.get('/reports/<id>/pdf')
@auth_required
def download_report(id):
    pdf_buffer = generate_report("Report", get_data(id))

    storage = get_storage()
    filename = f'reports/{id}.pdf'
    storage.upload(pdf_buffer, filename, content_type='application/pdf')

    url = storage.get_url(filename, expires_in=3600)
    return {'url': url}

Generating in the background

Rendering is slow enough to be worth moving off the request.

from feather import job

@job
def generate_report_async(report_id, user_id):
    pdf_buffer = generate_report("Report", get_data(report_id))
    storage = get_storage()
    filename = f'reports/{user_id}/{report_id}.pdf'
    storage.upload(pdf_buffer, filename, content_type='application/pdf')
    return {'filename': filename}

result = generate_report_async.enqueue(report_id, user_id)

Get started

Tutorial: build a Kanban app

Building the UI

Backend

Features

Tooling

Testing

Deployment

Basic usage

Saving to storage

Generating in the background

​Basic usage

​Saving to storage

​Generating in the background

Basic usage

Saving to storage

Generating in the background