Outputting CSV with Django¶

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Outputting CSV with Django¶

This document explains how to output CSV (Comma Separated Values) dynamically
using Django views. To do this, you can either use the Python CSV library or the
Django template system.

Using the Python CSV library¶

Python comes with a CSV library, csv. The key to using it with Django is
that the csv module’s CSV-creation capability acts on file-like objects,
and Django’s HttpResponse objects are file-like objects.

Here’s an example:

import csv
from django.http import HttpResponse

def some_view(request):
    # Create the HttpResponse object with the appropriate CSV header.
    response = HttpResponse(mimetype='text/csv')
    response['Content-Disposition'] = 'attachment; filename=somefilename.csv'

    writer = csv.writer(response)
    writer.writerow(['First row', 'Foo', 'Bar', 'Baz'])
    writer.writerow(['Second row', 'A', 'B', 'C', '"Testing"', "Here's a quote"])

    return response

The code and comments should be self-explanatory, but a few things deserve a
mention:

• The response gets a special MIME type, text/csv. This tells
  browsers that the document is a CSV file, rather than an HTML file. If
  you leave this off, browsers will probably interpret the output as HTML,
  which will result in ugly, scary gobbledygook in the browser window.
• The response gets an additional Content-Disposition header, which
  contains the name of the CSV file. This filename is arbitrary; call it
  whatever you want. It'll be used by browsers in the "Save as..."
  dialogue, etc.
• Hooking into the CSV-generation API is easy: Just pass response as the
  first argument to csv.writer. The csv.writer function expects a
  file-like object, and HttpResponse objects fit the
  bill.
• For each row in your CSV file, call writer.writerow, passing it an
  iterable object such as a list or tuple.
• The CSV module takes care of quoting for you, so you don't have to worry
  about escaping strings with quotes or commas in them. Just pass
  writerow() your raw strings, and it'll do the right thing.

Handling Unicode¶

Python's csv module does not support Unicode input. Since Django uses
Unicode internally this means strings read from sources such as
HttpRequest are potentially problematic. There are a few
options for handling this:

• Manually encode all Unicode objects to a compatible encoding.
• Use the UnicodeWriter class provided in the csv module's examples
  section.
• Use the python-unicodecsv module, which aims to be a drop-in
  replacement for csv that gracefully handles Unicode.

For more information, see the Python documentation of the csv module.

Using the template system¶

Alternatively, you can use the Django template system
to generate CSV. This is lower-level than using the convenient Python csv
module, but the solution is presented here for completeness.

The idea here is to pass a list of items to your template, and have the
template output the commas in a for loop.

Here's an example, which generates the same CSV file as above:

from django.http import HttpResponse
from django.template import loader, Context

def some_view(request):
    # Create the HttpResponse object with the appropriate CSV header.
    response = HttpResponse(mimetype='text/csv')
    response['Content-Disposition'] = 'attachment; filename=somefilename.csv'

    # The data is hard-coded here, but you could load it from a database or
    # some other source.
    csv_data = (
        ('First row', 'Foo', 'Bar', 'Baz'),
        ('Second row', 'A', 'B', 'C', '"Testing"', "Here's a quote"),
    )

    t = loader.get_template('my_template_name.txt')
    c = Context({
        'data': csv_data,
    })
    response.write(t.render(c))
    return response

The only difference between this example and the previous example is that this
one uses template loading instead of the CSV module. The rest of the code --
such as the mimetype='text/csv' -- is the same.

Then, create the template my_template_name.txt, with this template code:

{% for row in data %}"{{ row.0|addslashes }}", "{{ row.1|addslashes }}", "{{ row.2|addslashes }}", "{{ row.3|addslashes }}", "{{ row.4|addslashes }}"
{% endfor %}

This template is quite basic. It just iterates over the given data and displays
a line of CSV for each row. It uses the addslashes template filter to
ensure there aren't any problems with quotes.

Other text-based formats¶

Notice that there isn't very much specific to CSV here -- just the specific
output format. You can use either of these techniques to output any text-based
format you can dream of. You can also use a similar technique to generate
arbitrary binary data; see Outputting PDFs with Django for an example.