Error in Django when using matplotlib examples

Question

I am testing several cases of Django and matplotlib such as this question or in french.

Each time, it works on my mac, but does not on my server, where I receive the

Answer 1

At the moment, matplotlib's writing functions require the seek ducktype to use the response at a file. You can write to a buffer, like this:

import io

def mplimage(request):
    f = matplotlib.figure.Figure()

    # Code that sets up figure goes here; in the question, that's ...
    FigureCanvasAgg(f)

    buf = io.BytesIO()
    plt.savefig(buf, format='png')
    plt.close(f)
    response = HttpResponse(buf.getvalue(), content_type='image/png')
    return response

Answer 2

You can just replace the response with a buffer and then add the buffer to the response. This will give an appropriate object to canvas.print_png() and keep code changes to a minimum.

def mplimage(request):
    f = matplotlib.figure.Figure()
    buf = io.BytesIO()
    canvas = FigureCanvasAgg(f)
    canvas.print_png(buf)
    response=HttpResponse(buf.getvalue(),content_type='image/png')
    # if required clear the figure for reuse 
    f.clear()
    # I recommend to add Content-Length for Django
    response['Content-Length'] = str(len(response.content))
    #
    return response