A shamefull, bad, ugly and dirty script that will add the remaining entries for updating the plurals of a po file

update-po-plurals.py

#
import argparse
from sys import stdout 

parser = argparse.ArgumentParser(
	description='Updates the plural forms of a .po from initial to final')

parser.add_argument('pofile', type=str, help='Po file to be updated')

parser.add_argument("--from", type=int, dest='from_plural',
                    help="Initial number of plural forms")

parser.add_argument("--to", type=int, dest='to_plural',
                    help="Final number of plural forms")

args = parser.parse_args()

with open(args.pofile) as file:
	for line in file:
		stdout.write(line)
		if line.startswith("msgstr[%i]" % (args.from_plural - 1)):
			for i in range(args.from_plural, args.to_plural):
				stdout.write(("msgstr[%i] " % i) + line[10:])

Usage: python update-po-plurals.py your.po --from=N --to=M > your_new.po
(you will have to adjust manually the header, "nplurals=M")