Embedding a matplotlib plot within a django site

Question

When a user clicks the upload button to upload their csv my website should return a matplotlib plot. I have the plot saved to a buffer and it now just needs to display in the same page as where the upload button is.

I am a beginner to Django so the following is what I did (warning: some pseudocode ahead)

In views.py and yes I can see that the httprequest returned by plotResult(request, csvfile_path) doesn't interact with list.html. I'm not sure how to get it to

def list(request):
    #Working code for uploading a csv and retrieving the path to the uploaded file
    if document uploaded:
        return plotResult(request, csvfile_path)

    return render(
        request,
        'list.html',
        {'documents': documents, 'form': form}
    )

def plotResult(request, sorted_dir):
    # Bunch of code for computing the plot - functions in custom_script.py
    return Plot_Composite_metrics(bunch of parameters)

Plot_Composite_metrics is in custom_script.py which is in the same directory as views.py and contains many functions for computing the plot:

def Plot_Composite_metrics(bunch of parameters):
    # More code for computing the plot
    ax = plt.subplot2grid((3,4), (0,0), colspan=4)
    # Code for adding attributes to ax. 

    # Store the now built image in a string buffer
    buffer = StringIO.StringIO()
    canvas = pylab.get_current_fig_manager().canvas
    canvas.draw()
    pilImage = PIL.Image.fromstring("RGB", canvas.get_width_height(), canvas.tostring_rgb())
    pilImage.save(buffer, "PNG")
    pylab.cose()

    return HttpResponse(buffer.getvalue(), mimetype="image/png")

in list.html I have what I need to generate the upload functionality, the following to produce the matplotlib plot:

<img src="data:image/png;base64,{{graphic|safe}}">

When I run this there is no crash, the img tag above at first only has its empty filler. Then after uploading the website returns the plot, but on a page of its own instead of at the img tag below the upload button. How do I make it so that the matplotlib plot appears embedded on the same page?

If by any chance knowing what the plot looks like is important, here:

J.J. Hakala · Accepted Answer · 2016-01-23 09:41:08Z

2

I have saved my plots in SVG format for similar purpose,

import six

fig = plt.figure()
# plot some data
tmp = six.StringIO()
fig.savefig(tmp, format='svg', bbox_inches='tight')

template = loader.get_template('path_to_/template.html')
c = Context({ 'svg': tmp.getvalue() })
return HttpResponse(template.render(c))

In the template file,

{% if svg %}
<div style="width:60em;height:46em">
  {% autoescape off %}
  {{ svg }}
  {% endautoescape %}
</div>

answered Jan 23, 2016 at 9:41

J.J. Hakala

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