Python PO to CSV to PO roundtripping

csvpo.py

import unicodecsv as csv
import sys

import polib

def po2csv(po_file):
    po = polib.pofile(po_file)

    with open('messages.csv', 'wb') as csvfile:
        writer = csv.writer(csvfile)
        writer.writerow(['English'])

        for entry in po:
            writer.writerow([entry.msgid, entry.msgstr])

def csv2po(csv_file):
    po = polib.POFile()

    with open(csv_file) as csvfile:
        reader = csv.reader(csvfile)
        for row in reader:
            entry = polib.POEntry(
                msgid=row[0],
                msgstr=row[1]
            )
            po.append(entry)
    po.save('out.po')

if __name__ == '__main__':
    if len(sys.argv) < 3:
        print('Usage: {} <po2csv|csv2po> <input_file>'.format(sys.argv[0]))
        sys.exit(1)
    if sys.argv[1] == 'po2csv':
        po2csv(sys.argv[2])
    elif sys.argv[1] == 'csv2po':
        csv2po(sys.argv[2])

requirements.txt

polib
unicodecsv

Replace:
writer.writerow([entry.msgid])
By:
writer.writerow([entry.msgid, entry.msgstr])

Good catch! Updated.