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 PDF library.
The advantage of generating PDF files dynamically is that you can create customized PDFs for different purposes – say, for different users or different pieces of content.
For example, Django was used at kusports.com to generate customized, printer-friendly NCAA tournament brackets, as PDF files, for people participating in a March Madness contest.
The ReportLab library is available on PyPI. A user guide (not
coincidentally, a PDF file) is also available for download.
You can install ReportLab with
$ pip install reportlab
...\> 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 API
acts on file-like objects, and Django’s
objects 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. return FileResponse(buffer, as_attachment=True, filename='hello.pdf')
The code and comments should be self-explanatory, but a few things deserve a mention:
- The response will automatically set the MIME type application/pdf based on the filename extension. This tells browsers that the document is a PDF file, rather than an HTML file or a generic application/octet-stream binary content.
as_attachment=Trueis passed to
FileResponse, it sets the appropriate
Content-Dispositionheader and that tells Web browsers to pop-up a dialog box prompting/confirming how to handle the document even if a default is set on the machine. If the
as_attachmentparameter is omitted, browsers will handle the PDF using whatever program/plugin they’ve been configured to use for PDFs.
- You can provide an arbitrary
filenameparameter. It’ll be used by browsers in the “Save as…” dialog.
- Hooking into the ReportLab API is easy: The same buffer passed as the first
canvas.Canvascan be fed to the
- Note that all subsequent PDF-generation methods are called on the PDF
object (in this case,
p) – not on
- Finally, it’s important to call
save()on the PDF file.
ReportLab is not thread-safe. Some of our users have reported odd issues with building PDF-generating Django views that are accessed by many people at the same time.
Notice that there isn’t a lot in these examples that’s PDF-specific – just the
reportlab. You can use a similar technique to generate any
arbitrary format that you can find a Python library for. Also see
Outputting CSV with Django for another example and some techniques you can use
when generated text-based formats.
Django Packages provides a comparison of packages that help generate PDF files from Django.