Statement PDFs in Django

Why statements become PDFs

A statement summarises a period that is now closed. Regenerating it later from live data would produce a different document, which defeats the point. That is the difference between a document and a view of a database, and it is why finance and account management keep asking for this.

What a statement has to carry

Before any of the code below matters, the template has to produce a document that is actually a statement. These are the fields that make it one, and the ones a reader or an auditor will look for first.

• the opening balance and the closing balance
• every transaction in the period with date, description and signed amount
• a running balance column, so a reader can find where a discrepancy starts
• the account identifier, usually masked
• the statement period, which must not overlap the previous one

Turning your the Django template language template into a document

You already have the markup. Render_to_string("invoices/detail.html", context) gives you it as a string, which is the only input the render needs. Django resolves {% static %} to a path relative to STATIC_URL, which means the stylesheet URL in your rendered HTML is only meaningful to a browser that already has a session on your host. A renderer fetching it from outside gets a 404 and produces an unstyled document. Inline the CSS into the string you send, or make STATIC_URL absolute for this one code path.

The Django implementation

httpx is the client most projects here already have. The render happens in a view that returns FileResponse, and you hand the bytes back as a FileResponse with an explicit content type.

# views.py
import httpx
from django.conf import settings
from django.http import FileResponse
from django.shortcuts import get_object_or_404
from django.template.loader import render_to_string

from .models import Statement


def statement_pdf(request, pk):
    statement = get_object_or_404(Statement, pk=pk)

    # A template that extends nothing. The on-screen template carries base.html,
    # the nav and the messages block, none of which belong in a statement.
    html = render_to_string("statements/pdf.html", {"statement": statement})

    upstream = httpx.stream(
        "POST",
        "https://api.pdfpipe.xyz/v1/pdf",
        headers={"Authorization": f"Bearer {settings.PDFPIPE_KEY}"},
        json={"html": html, "options": {"format": "A4", "printBackground": True}},
        timeout=60.0,
    )

    response = upstream.__enter__()
    response.raise_for_status()

    return FileResponse(
        response.iter_bytes(),
        content_type="application/pdf",
        filename=f"statement-{statement.reference}.pdf",
    )

The CSS that makes a statement page correctly

The layout problem specific to this document is that a long transaction table spanning many pages, needing repeated headers and a running balance that stays legible after a break. These rules handle it.

/* Line items run past one page. Repeat the header, keep the
   totals block whole, and never strand a single row. */
thead { display: table-header-group; }
tfoot { display: table-footer-group; }
tr    { break-inside: avoid; }

.totals {
  break-inside: avoid;
  break-before: auto;
}

@page {
  size: A4;
  margin: 18mm 16mm 22mm;
}

What goes wrong in Django

The template that renders your on-screen view is almost always the wrong one to send. It carries the base layout, the nav, and the messages framework, all of which land in the PDF. Render a template that extends nothing, and keep it beside the view template so the two do not drift.

What people try first

Most Django projects reach for WeasyPrint or xhtml2pdf, both of which put layout in your Python process. WeasyPrint needs Cairo and Pango in the image; xhtml2pdf supports a subset of CSS that stopped growing years ago. That works until it is running on more than one machine, at which point the browser becomes the thing you operate rather than the thing you use.

Where the statement lives afterwards

Rendering is the short part. Statements are the document most often requested again years later, usually for a loan application or an audit. Regenerating one from current data would produce different figures, so the rendered file is the record and has to be stored as issued.

Getting the document right

• Check the closing balance, which has to reconcile with the transactions listed above it.
• Generation is triggered by the end of a billing or accounting period, so size the timeout for that path rather than for a health check.
• This is a batch shape: render the run through the batch endpoint rather than firing thousands of individual requests.
• Backgrounds are painted by default here, so a design that uses colour needs nothing set. Only an explicit print_background of false turns them off.

Frequently asked

Related

Other Django documents, and the same statement in other stacks.