1 ==========================

     2 Outputting CSV with Django

     3 ==========================

     4 

     5 This document explains how to output CSV (Comma Separated Values) dynamically

     6 using Django views.

     7 

     8 To do this, you can either use the `Python CSV library`_ or the Django template

     9 system.

    10 

    11 .. _Python CSV library: http://www.python.org/doc/current/lib/module-csv.html

    12 

    13 Using the Python CSV library

    14 ============================

    15 

    16 Python comes with a CSV library, ``csv``. The key to using it with Django is

    17 that the ``csv`` module's CSV-creation capability acts on file-like objects,

    18 and Django's ``HttpResponse`` objects are file-like objects.

    19 

    20 .. admonition:: Note

    21 

    22     For more information on ``HttpResponse`` objects, see

    23     `Request and response objects`_.

    24 

    25     For more information on the CSV library, see the `CSV library docs`_.

    26 

    27     .. _Request and response objects: ../request_response/

    28     .. _CSV library docs: http://www.python.org/doc/current/lib/module-csv.html

    29 

    30 Here's an example::

    31 

    32     import csv

    33     from django.http import HttpResponse

    34 

    35     def some_view(request):

    36         # Create the HttpResponse object with the appropriate CSV header.

    37         response = HttpResponse(mimetype='text/csv')

    38         response['Content-Disposition'] = 'attachment; filename=somefilename.csv'

    39 

    40         writer = csv.writer(response)

    41         writer.writerow(['First row', 'Foo', 'Bar', 'Baz'])

    42         writer.writerow(['Second row', 'A', 'B', 'C', '"Testing"', "Here's a quote"])

    43 

    44         return response

    45 

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

    47 mention:

    48 

    49     * The response gets a special mimetype, ``text/csv``. This tells

    50       browsers that the document is a CSV file, rather than an HTML file. If

    51       you leave this off, browsers will probably interpret the output as HTML,

    52       which will result in ugly, scary gobbledygook in the browser window.

    53 

    54     * The response gets an additional ``Content-Disposition`` header, which

    55       contains the name of the CSV file. This filename is arbitrary; call it

    56       whatever you want. It'll be used by browsers in the "Save as..."

    57       dialogue, etc.

    58 

    59     * Hooking into the CSV-generation API is easy: Just pass ``response`` as

    60       the first argument to ``csv.writer``. The ``csv.writer`` function expects

    61       a file-like object, and ``HttpResponse`` objects fit the bill.

    62 

    63     * For each row in your CSV file, call ``writer.writerow``, passing it an

    64       iterable object such as a list or tuple.

    65 

    66     * The CSV module takes care of quoting for you, so you don't have to worry

    67       about escaping strings with quotes or commas in them. Just pass

    68       ``writerow()`` your raw strings, and it'll do the right thing.

    69 

    70 Using the template system

    71 =========================

    72 

    73 Alternatively, you can use the `Django template system`_ to generate CSV. This

    74 is lower-level than using the convenient CSV, but the solution is presented

    75 here for completeness.

    76 

    77 The idea here is to pass a list of items to your template, and have the

    78 template output the commas in a ``{% for %}`` loop.

    79 

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

    81 

    82     from django.http import HttpResponse

    83     from django.template import loader, Context

    84 

    85     def some_view(request):

    86         # Create the HttpResponse object with the appropriate CSV header.

    87         response = HttpResponse(mimetype='text/csv')

    88         response['Content-Disposition'] = 'attachment; filename=somefilename.csv'

    89 

    90         # The data is hard-coded here, but you could load it from a database or

    91         # some other source.

    92         csv_data = (

    93             ('First row', 'Foo', 'Bar', 'Baz'),

    94             ('Second row', 'A', 'B', 'C', '"Testing"', "Here's a quote"),

    95         )

    96 

    97         t = loader.get_template('my_template_name.txt')

    98         c = Context({

    99             'data': csv_data,

   100         })

   101         response.write(t.render(c))

   102         return response

   103 

   104 The only difference between this example and the previous example is that this

   105 one uses template loading instead of the CSV module. The rest of the code --

   106 such as the ``mimetype='text/csv'`` -- is the same.

   107 

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

   109 

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

   111     {% endfor %}

   112 

   113 This template is quite basic. It just iterates over the given data and displays

   114 a line of CSV for each row. It uses the `addslashes template filter`_ to ensure

   115 there aren't any problems with quotes. If you can be certain your data doesn't

   116 have single or double quotes in it, you can remove the ``addslashes`` filters.

   117 

   118 .. _Django template system: ../templates/

   119 .. _addslashes template filter: ../templates/#addslashes