diff -r 261778de26ff -r 620f9b141567 thirdparty/google_appengine/lib/django/docs/outputting_csv.txt --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/thirdparty/google_appengine/lib/django/docs/outputting_csv.txt Tue Aug 26 21:49:54 2008 +0000 @@ -0,0 +1,119 @@ +========================== +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. + +.. _Python CSV library: http://www.python.org/doc/current/lib/module-csv.html + +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. + +.. admonition:: Note + + For more information on ``HttpResponse`` objects, see + `Request and response objects`_. + + For more information on the CSV library, see the `CSV library docs`_. + + .. _Request and response objects: ../request_response/ + .. _CSV library docs: http://www.python.org/doc/current/lib/module-csv.html + +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 mimetype, ``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. + +Using the template system +========================= + +Alternatively, you can use the `Django template system`_ to generate CSV. This +is lower-level than using the convenient CSV, 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. If you can be certain your data doesn't +have single or double quotes in it, you can remove the ``addslashes`` filters. + +.. _Django template system: ../templates/ +.. _addslashes template filter: ../templates/#addslashes