[Csv] Re: First Cut at CSV PEP

[Skip Montanaro]

    Dave> The None thing and the implicit __str__ conversion is there in the
    Dave> Object Craft parser to be compatible with the DB-API....

Hmmm...  I've used MySQLdb and psycopg and don't recall my queries returning
None.  (He furiously searches for None in PEP 249...)  Ah, I see:

    SQL NULL values are represented by the Python None singleton on input
    and output.

I generally have always defined my fields to have defaults and usually also
declare them NOT NULL, so I wouldn't expect to see None in my query results.

Still, the current treatment of None doesn't successfully round-trip
("select * ...", dump to csv, load from csv, repopulate database).  Do you
distinguish an empty field from a quoted field printed as ""?  That is, are
these output rows different?

    5.0,,"Mary, Mary, quite contrary"\r\n
    5.0,"","Mary, Mary, quite contrary"\r\n

the former parsing into

    [5.0, None, "Mary, Mary, quite contrary"]

and the latter into

    [5.0, "", "Mary, Mary, quite contrary"]

?

    Dave> Now without the implicit __str__ and conversion of None to '' we
    Dave> would require a shirtload of code to do the same thing, only it
    Dave> would be as slow as a slug on valium.

How about we let the user define how to handle None?  I would always want
None's appearing in my data to raise and exception.  You clearly have a use
case for automatically mapping to the empty string.

Skip