First Cut at CSV PEP

[Skip Montanaro]

    Cliff> It's also debatable whether the numbers should have been returned
    Cliff> as strings or numbers.  I lean towards the former, as csv is a
    Cliff> text format and can't convey this sort of information by itself,
    Cliff> which is why I chose to return only strings, including the empty
    Cliff> string for an empty field rather than None.  I agree with Kevin
    Cliff> that this is best left to application logic rather than the
    Cliff> module.

I think returning strings is more Pythonic (explicit is better than
implicit), while returning numbers is more Perlish.  There's no particular
reason the user couldn't specify a set of type converters to filter the
input rows, e.g.:

    [int, int, str, mxDateTime.DateTimeFromString, ...]

but she could do that just as easily herself:

    reader = csv.reader(open("some.csv")):
    for row in reader:
        for i in range(min(len(rowtypes), len(row))):
            row[i] = rowtypes[i](row[i])

or something similar.  Here again we get into the sticky issue of row
length, suggesting we should just pass the buck to the caller.

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