How to check whether csv.DictReader object is empty or not

I am writing python code to read contents from a csv file with the DictReader.

with open(parafile, "rb") as paracsv:         
    #Read in parameter values as a dictionary
    paradict = csv.DictReader(paracsv)
    if paradict.line_num <= 1:
        return None

I want to be able to return immediately if there is no more than one row read from the csv file.

I have tried checking the line_num, but it always returns 0 even there are more than one row in the file. Does anyone know what is the correct/efficient way to check this?

Thanks

Solution

You cannot, without reading lines, know how many there are in the file. Note that the csvreader.line_num attribute reflects the number of lines read so far, not the number of lines present in the file:

The number of lines read from the source iterator. This is not the same as the number of records returned, as records can span multiple lines.

Just read your file; if there is only one row in the file, you'll end up returning early anyway.

If you only return None if there were no rows read, you could use:

with open(parafile, "rb") as paracsv:         
    #Read in parameter values as a dictionary
    paradict = csv.DictReader(paracsv)
    has_rows = False
    for line in paradict:
        has_rows = True

    if not has_rows:
        return None

If there are no rows beyond the first header row in the file, this returns early, as the for loop immediately terminates.