First Cut at CSV PEP

[Kevin Altis]

> I'm ready to toddle off to bed, so I'm stopping here for tonight.
>  Attached
> is what I've come up with so far in the way of a PEP.  Feel free to flesh
> out, rewrite or add new sections.  After a brief amount of cycling, I'll
> check it into CVS.

Probably need to specify that input and output deals with string
representations, but there are some differences:

[[5,'Bob',None,1.0]]

DSV.exportCSV produces

'5,Bob,None,1.0'

Data that doesn't need quoting isn't quoted. Assuming those were spreadsheet
values with the third item just an empty cell, then using Excel export rules
would result in a default CSV of

5,Bob,,1\r\n

None is just an empty field. In Excel, the number 1.0 is just 1 in the
exported file, but that may not matter, we can export 1.0 for the field.
This reminds me that the boundary case of the last record just having EOF
with no line ending should be tested.

Importing this line with importDSV for example yields a list of lists.

[['5', 'Bob', '', '1']]

Its debatable whether the third field should be None or an empty string.
Further interpretation of each field becomes application-specific. The API
makes it easy to do further processing as each row is read.

I'm still not sure about some of the database CSV handling issues, often it
seems they want a string field to be quoted regardless of whether it
contains a comma or newlines, but number and empty field should not be
quoted. It is certainly nice to be able to import a file that contains

5,"Bob",,1.0\r\n

and not need to do any further translation. Excel appears to interpret
quoted numbers and unquoted numbers as numeric fields when importing.

Just trying to be anal-retentive here to make sure all the issues are
covered ;-)

ka