Outputting PDFs with Django

Outputting PDFs with Django

This document explains how to output PDF files dynamically using Django views.This is made possible by the excellent, open-source ReportLab Python PDFlibrary.

The advantage of generating PDF files dynamically is that you can createcustomized PDFs for different purposes – say, for different users or differentpieces of content.

For example, Django was used at kusports.com to generate customized,printer-friendly NCAA tournament brackets, as PDF files, for peopleparticipating in a March Madness contest.

Install ReportLab

The ReportLab library is available on PyPI. A user guide (notcoincidentally, a PDF file) is also available for download.You can install ReportLab with pip:

/

$ python -m pip install reportlab

...\> py -m pip install reportlab

Test your installation by importing it in the Python interactive interpreter:

>>> import reportlab

If that command doesn’t raise any errors, the installation worked.

Write your view

The key to generating PDFs dynamically with Django is that the ReportLab APIacts on file-like objects, and Django’s FileResponseobjects accept file-like objects.

Here’s a “Hello World” example:

import io
from django.http import FileResponse
from reportlab.pdfgen import canvas
 
def some_view(request):
    # Create a file-like buffer to receive PDF data.
    buffer = io.BytesIO()
 
    # Create the PDF object, using the buffer as its "file."
    p = canvas.Canvas(buffer)
 
    # Draw things on the PDF. Here's where the PDF generation happens.
    # See the ReportLab documentation for the full list of functionality.
    p.drawString(100, 100, "Hello world.")
 
    # Close the PDF object cleanly, and we're done.
    p.showPage()
    p.save()
 
    # FileResponse sets the Content-Disposition header so that browsers
    # present the option to save the file.
    buffer.seek(0)
    return FileResponse(buffer, as_attachment=True, filename='hello.pdf')

The code and comments should be self-explanatory, but a few things deserve amention:

The response will automatically set the MIME type _application/pdf_based on the filename extension. This tells browsers that the document is aPDF file, rather than an HTML file or a generic _application/octet-stream_binary content.
When as_attachment=True is passed to FileResponse, it sets theappropriate Content-Disposition header and that tells Web browsers topop-up a dialog box prompting/confirming how to handle the document even if adefault is set on the machine. If the as_attachment parameter is omitted,browsers will handle the PDF using whatever program/plugin they’ve beenconfigured to use for PDFs.
You can provide an arbitrary filename parameter. It’ll be used by browsersin the “Save as…” dialog.
You can hook into the ReportLab API: The same buffer passed as the firstargument to canvas.Canvas can be fed to theFileResponse class.
Note that all subsequent PDF-generation methods are called on the PDFobject (in this case, p) – not on buffer.
Finally, it’s important to call showPage() and save() on the PDFfile.

Note

ReportLab is not thread-safe. Some of our users have reported odd issueswith building PDF-generating Django views that are accessed by many peopleat the same time.

Other formats

Notice that there isn’t a lot in these examples that’s PDF-specific – just thebits using reportlab. You can use a similar technique to generate anyarbitrary format that you can find a Python library for. Also seeOutputting CSV with Django for another example and some techniques you can usewhen generated text-based formats.