Results display using matplotlib

The matplotlib library provides another alternative for generating charts from Python. It can be found on the Python Package Index site, http://pypi.python.org/pypi/matplotlib. The version of matplotlib used in this chapter is 0.98.3.

With matplotlib, our application cannot simply construct a URL and push the task of generating and serving the image data off to another host. Instead, we need to write a view that will generate and serve the image data. After some investigation of the matplotlib APIs, an initial implementation (in survey/views.py) might be:

from django.http import HttpResponse 
from survey.models import Question 
from matplotlib.figure import Figure 
from matplotlib.backends.backend_agg import FigureCanvasAgg as \FigureCanvas 

@log_view 
def answer_piechart(request, pk): 
    q = get_object_or_404(Question, pk=pk) 
    answer_set = q.answer_set.all() 
    x = [a.votes for a in answer_set] 
    labels = [a.answer for a in answer_set] 

    fig...