Question

I have a django view that I want to return an Excel file. The code is below:

def get_template(request, spec_pk):
    spec = get_object_or_404(Spec, pk=spec_pk)

    response = HttpResponse(spec.get_template(), mimetype='application/ms-excel')
    response['Content-Disposition'] = 'attachment; filename=%s_template.xls' % spec.name
    return response

In that example, the type of spec.get_template() is <type 'bytearray'> which contains the binary data of an Excel spreadsheet.

The problem is, when I try to download that view, and open it with Excel, it comes in as garbled binary data. I know that the bytearray is correct though, because if I do the following:

f = open('temp.xls', 'wb')
f.write(spec.get_template())

I can open temp.xls in the Excel perfectly.

I’ve even gone so far as to modify my view to:

def get_template(request, spec_pk):
    spec = get_object_or_404(Spec, pk=spec_pk)
    f = open('/home/user/temp.xls', 'wb')
    f.write(spec.get_template())
    f.close()

    f = open('/home/user/temp.xls', 'rb')
    response = HttpResponse(f.read(), mimetype='application/ms-excel')
    response['Content-Disposition'] = 'attachment; filename=%s_template.xls' % spec.name
    return response

And it works perfectly- I can open the xls file from the browser into Excel and everything is alright.

So my question is- what do I need to do that bytearray before I pass it to the HttpResponse. Why does saving it as binary, then re-opening it work perfectly, but passing the bytearray itself results in garbled data?

Answer 1

Okay, through completely random (and very persistent) trial and error, I found a solution using the python binascii module.

This works:

response = HttpResponse(binascii.a2b_qp(spec.get_template()), mimetype='application/ms-excel')

According to the python docs for binascii.a2b_qp:

Convert a block of quoted-printable data back to binary and return the binary data. More than one line may be passed at a time. If the optional argument header is present and true, underscores will be decoded as spaces.

Would love for someone to tell me why saving it as binary, then reopening it worked though.