Confused about making a CSV file into a ZIP file in django

Question

I have a view that takes data from my site and then makes it into a zip compressed csv file. Here is my working code sans zip:

def backup_to_csv(request):
    response = HttpResponse(mimetype='text/csv')
    response['Content-Disposition'] = 'attachment; filename=backup.csv'

    writer = csv.writer(response, dialect='excel')

    #code for writing csv file go here...

    return response

and it works great. Now I want that file to be compressed before it gets sent out. This is where I get stuck.

def backup_to_csv(request):

    output = StringIO.StringIO() ## temp output file
    writer = csv.writer(output, dialect='excel')

    #code for writing csv file go here...

    response = HttpResponse(mimetype='application/zip')
    response['Content-Disposition'] = 'attachment; filename=backup.csv.zip'

    z = zipfile.ZipFile(response,'w')   ## write zip to response
    z.writestr("filename.csv", output)  ## write csv file to zip

    return response

But thats not it and I have no idea how to do this.

Answer 1

OK I got it. Here is my new function:

def backup_to_csv(request):

    output = StringIO.StringIO() ## temp output file
    writer = csv.writer(output, dialect='excel')

    #code for writing csv file go here...

    response = HttpResponse(mimetype='application/zip')
    response['Content-Disposition'] = 'attachment; filename=backup.csv.zip'

    z = zipfile.ZipFile(response,'w')   ## write zip to response
    z.writestr("filename.csv", output.getvalue())  ## write csv file to zip

    return response

Answer 2

Note how, in the working case, you return response... and in the NON-working case you return z, which is NOT an HttpResponse of course (while it should be!).

So: use your csv_writer NOT on response but on a temporary file; zip the temporary file; and write THAT zipped bytestream into the response!

Answer 3

zipfile.ZipFile(response,'w') 

doesn't seem to work in python 2.7.9. The response is a django.HttpResponse object (which is said to be file-like) but it gives an error "HttpResponse object does not have an attribute 'seek'. When the same code is run in python 2.7.0 or 2.7.6 (I haven't tested it in other versions) it is OK... So you'd better test it with python 2.7.9 and see if you get the same behaviour.