Find number of columns in csv file

Question

My program needs to read csv files which may have 1,2 or 3 columns, and it needs to modify its behaviour accordingly. Is there a simple way to check the number of columns withou

Answer 1

What happens if the user provides you with a CSV file with fewer columns? Are default values used instead?

If so, why not extend the row with null values instead?

reader = csv.reader(f,delimiter=d)
for row in reader:
    row += [None] * (3 - len(row))
    try:
        foo, bar, baz = row
    except ValueError:
        # Too many values to unpack: too many columns in the CSV
        raise CSVError("Too many columns in input file.")

Now bar and baz will at least be None and the exception handler will take care of any rows longer than 3 items.