sort csv by fieldnames and write a new csv file

import csv
from pathlib import Path
import sys


def sort_csv(file):
    '''
    This function sorts csv file alphabetical by header.
    The output is written to the file new_ + filename
    The dialect should be detected automatically.
    '''
    sniffer = csv.Sniffer()
    source = Path(file)
    destination = source.with_name('new_' + source.stem).with_suffix(source.suffix)
    with source.open() as fd_in, destination.open('w') as fd_out:
        dialect = sniffer.sniff(fd_in.read(2048))
        fd_in.seek(0)
        reader = csv.DictReader(fd_in, dialect=dialect)
        fields = sorted(reader.fieldnames)
        writer = csv.DictWriter(fd_out, fields, dialect=dialect)
        writer.writeheader()
        for row in reader:
            writer.writerow(row)


if __name__ == '__main__':
    if len(sys.argv) == 2:
        try:
            sort_csv(sys.argv[1])
        except Exception as e:
            print('Got the exception:', e, file=sys.stderr)
        sys.exit(0)
    else:
        print(f'{sys.argv[0]} source_file.csv', file=sys.stderr)
        sys.exit(1)