Save Matplotlib plot image into Django model

There are several problems with your code:

• You should not save the figure to a StringIO but instead, a io.BytesIO(). This is because the contents of the PNG file isn't human-readable text but binary data.

• Another problem is how you handle the BytesIO (StringIO in your code) when passing it to savefig. A BytesIO isn't associated with a file (that's the whole point of having an in-memory file-like object), so it doesn't have a file name – which is what I suppose you want to get at by that u'%s' % figure expression. Instead, just write to the file-like object itself.

• Third, use a django.core.files.images.ImageFile instead of ContentFile. Also, initialise it with the BytesIO object itself, not its bytes value.

The relevant portion of your code then becomes:

figure = io.BytesIO()plt.plot(xvalues, yvalues)plt.savefig(figure, format="png")content_file = ImageFile(figure)

you might also want to try the plotly library - they have a js script that you can add to the html (https://plot.ly/javascript/getting-started/) and you can always serialize the arrays needing to be imported into the graph