Returning values from .writerow()

[jdotjdot]

In my Django project, I ran into the (admittedly niche) use case of needing to stream a large CSV file. Django offers a tutorial about how to do this, and it involves creating a fake buffer of sorts to return values from the csv writer rather than write to the actual buffer:

class Echo(object):
    """An object that implements just the write method of the file-like
    interface.
    """
    def write(self, value):
        """Write the value by returning it, instead of storing in a buffer."""
        return value

def some_streaming_csv_view(request):
    """A view that streams a large CSV file."""
    # Generate a sequence of rows. The range is based on the maximum number of
    # rows that can be handled by a single sheet in most spreadsheet
    # applications.
    rows = (["Row {0}".format(idx), str(idx)] for idx in range(65536))
    pseudo_buffer = Echo()
    writer = csv.writer(pseudo_buffer)
    response = StreamingHttpResponse((writer.writerow(row) for row in rows),
                                     content_type="text/csv")
    response['Content-Disposition'] = 'attachment; filename="somefilename.csv"'
    return response

I have non-ASCII characters in my data and needed to use the unicodecsv module and noticed that unicodecsv's writerow() method did not return anything. Adding a return statement fixed my problem. Even if only to better match the native Python csv module, I think this should be added.

Note that writerows() still doesn't properly return anything, but it also does not in the native Python csv module, and so I've left it for consistency's sake.

[jdotjdot]

By the way, the test failures here are part of the main code, not anything I added--it's an except: syntax issue for Python 3:

[mic159]

Yes, even master is failing. PR #26 fixes that.