Django view serving dynamically generated PDF files.

Serving static files is cool. However, static files have a drawback - mainly they tend to be static. I'm not saying that you should avoid serving static content or anything similar - static files have variety of important applications , which are not the topic of this post.

So what can you do when you want to serve a dynamically generated PDF file to the user? First of all you have to provide a package capable of generating such files, so unless you want to spend quite a few days implementing your own tool, you should try using ReportLab. ReportLab is quite powerful, but it takes a lot of effort to create a good layout. If you also want your PDF file to look sexy - you should choose pisa (it requires ReportLab as a dependency). Pisa is a HTML/CSS to PDF converter - which is just what we need (be warned - not all CSS styles are supported, but that's another history).

Let's have a look at this code:


  1 import ho.pisa
  2 import cStringIO
  3
  4 from django.http import HttpResponse
  5 from django.template.loader import get_template
  6 from django.template import Context
  7
  8    
  9 def generate_pdf(template_file, context={}):
 10     #to avoid using a temporary file StringIO has to be used
 11     pdf = cStringIO.StringIO()
 12     template = get_template(template_file)
 13    
 14     html_response  = template.render(Context(context))
 15    
 16     pdf_status = ho.pisa.pisaDocument(cStringIO.StringIO(html_response), pdf)
 17    
 18     if pdf_status.err:
 19         #catch it in the invoking view
 20         raise Exception('Oops! Something went wrong!')
 21     return HttpResponse(pdf.getvalue(), mimetype='application/pdf')
 
 This is a generic function that can render any template with an apropriate context and return a HttpResponse, this function may be used the following way:

 24 def generate_report_view(request):
 25     '''
 26         (...) some code
 27     '''
 28     return generate_pdf('reports/sample_report.html',\
 29         {'owner' : request.user, 'some_param' : 'Hello PDF Generator'})

There are two tricks here, that enable downloading the generated PDF directly from the view. Firstly, the cStringIO (faster version of StringIO) is used instead of a file, so that we do not have to make any HDD IO operations. Secondly we set the response mimetype to application/pdf, which informs a browser that this is not a regular site.

~KR