How to generate a file without saving it to disk in python?

Question

I'm using Python 2.7 and Django 1.7.

I have a method in my admin interface that generates some kind of a csv file.

def generate_csv(args):
    ...
    #some code that generates a dictionary to be written as csv
    ....

    # this creates a directory and returns its filepath
    dirname = create_csv_dir('stock')

    csvpath = os.path.join(dirname, 'mycsv_file.csv')
    fieldnames = [#some field names]

    # this function creates the csv file in the directory shown by the csvpath
    newcsv(data, csvheader, csvpath, fieldnames)

    # this automatically starts a download from that directory
    return HttpResponseRedirect('/media/csv/stock/%s' % csvfile)

All in all I create a csv file, save it somewhere on the disk, and then pass its URL to the user for download.

I was thinking if all this can be done without writing to disc. I googled around a bit and maybe content disposition attachment might help me, but I got lost in documentation a bit.

Anyway if there's an easier way of doing this I'd love to know.

Looks like this is very similar to the question here as it pretty much the same thing, just different payloads: http://stackoverflow.com/questions/908258/generating-file-to-download-with-django — Ragora, Sep 17 '15 at 15:46

score 13 · Accepted Answer · edited Sep 13 '21 at 14:20

13

Thanks to @Ragora, you pointed me towards the right direction.

I rewrote the newcsv method:

from io import StringIO
import csv


def newcsv(data, csvheader, fieldnames):
    """
    Create a new csv file that represents generated data.
    """
    new_csvfile = StringIO.StringIO()
    wr = csv.writer(new_csvfile, quoting=csv.QUOTE_ALL)
    wr.writerow(csvheader)
    wr = csv.DictWriter(new_csvfile, fieldnames = fieldnames)

    for key in data.keys():
        wr.writerow(data[key])

    return new_csvfile

and in the admin:

csvfile = newcsv(data, csvheader, fieldnames)

response = HttpResponse(csvfile.getvalue(), content_type='text/csv')
response['Content-Disposition'] = 'attachment; filename=stock.csv'
return response

edited Sep 13 '21 at 14:20

Preston Badeer

2,658
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answered Sep 17 '15 at 16:40

Saša Kalaba

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Thanks, but how import `StringIO`? [This](https://stackoverflow.com/questions/11914472/stringio-in-python3) does not help – Timo Nov 27 '17 at 16:44
1

try io.StringIO – hounded Oct 20 '20 at 21:17

score -2 · Answer 2 · answered Sep 17 '15 at 15:45

If it annoys you that you are saving a file to disk, just add the application/octet-stream content-type to the Content-Disposition header then delete the file from disk.

If this header (Content-Disposition) is used in a response with the application/octet- stream content-type, the implied suggestion is that the user agent should not display the response, but directly enter a `save response as...' dialog.

How to generate a file without saving it to disk in python?

2 Answers2

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