I did a search on Google code for the DictReader constructor.  I
analyzed the first 3 pages, the fieldnames parameter was used in 14 of
27 cases (discounting unittest code built into Python) and was not
used in 13 of 27 cases.  I suppose that means headered csv files are
sufficiently rare that they shouldn't be created implicitly by
default.  I still don't like the lack of symmetry of supporting
implicit header reads, but not implicit header writes.

On Thu, Feb 26, 2009 at 8:00 PM, Skip Montanaro <report@bugs.python.org> wrote:
>
> Skip Montanaro <skip@pobox.com> added the comment:
>
> More concretely, I don't think this is so onerous:
>
>    names = ["col1", "col2", "color"]
>    writer = csv.DictWriter(open("f.csv", "wb"), fieldnames=names, ...)
>    writer.writerow(dict(zip(names, names)))
>    ...
>
> or
>
>    f = open("f.csv", "rb")
>    names = csv.reader(f).next()
>    reader = csv.DictReader(f, fieldnames=names, ...)
>    ...
>
> Skip
>
> _______________________________________
> Python tracker <report@bugs.python.org>
> <http://bugs.python.org/issue1818>
> _______________________________________
>