Simple template for a python script that uses argparse and reads in and prints out a CSV or TSV

csv-script.py

import csv

def run(infile, outfile, is_tsv=False, dry_run=False):
    dialect = 'excel-tab' if is_tsv else 'excel'
    reader = csv.DictReader(infile, dialect=dialect)

    writer = None
    is_first = True

    for row in reader:
        if is_first:
            # only write to writer if there is any data in reader
            is_first = False
            fieldnames = reader.fieldnames
            writer = csv.DictWriter(outfile, fieldnames=fieldnames)
            writer.writeheader()

        writer.writerow(row)
        
##

def main():
    import argparse
    import sys
    parser = argparse.ArgumentParser(description='Parse CSV file')
    parser.add_argument('infile', nargs='?', type=argparse.FileType('r'),
                        default=sys.stdin, help='input file or stdin')
    parser.add_argument('outfile', nargs='?', type=argparse.FileType('w'),
                        default=sys.stdout, help='output file or stdout')
    parser.add_argument('--tsv', '-t', action='store_true', default=False)
    parser.add_argument('--dry-run', '-n', action='store_true', default=False)
    args = parser.parse_args()
    run(args.infile, args.outfile, args.tsv, args.dry_run)

if __name__ == '__main__':
    main()

# NOTE: if _csv.Error field larger than field limit
# take a look at https://stackoverflow.com/a/15063941/376489
# and maybe set `csv.field_size_limit(sys.maxsize)`
#