French postal codes

pcodes.py

#! /usr/bin/env python
#-*- coding: utf-8 -*-

import sys
import csv
import urllib2
from contextlib import contextmanager

POSTAL_CODES = "https://www.data.gouv.fr/s/resources/base-officielle-des-codes-postaux/20141106-120608/code_postaux_v201410.csv"

@contextmanager
def open_url(url):
    try:
        f = urllib2.urlopen(url)
    except IOError as err:
        yield None, err
    else:
        try:
            yield f, None
        finally:
            f.close()

def usage():
    print "This script takes one argument."
    print "Usage:"
    print "\tpcodes.py city"
    exit(1)

if __name__ == "__main__":
    # Point of entry in execution mode.
    if len(sys.argv) != 2:
        usage()

    city = sys.argv[1]

    with open_url(POSTAL_CODES) as (postal_codes, err):
        if err:
            print err
        else:
            dialect = csv.Sniffer().sniff(postal_codes.read(1024))
            rows = csv.reader(postal_codes, dialect)
            result = sorted([(row[1], row[2]) for row in rows
                                    if city.lower() in row[1].lower()],
                            key=lambda x: x[0])
            print "\n".join([value + " " + key for key, value in result])