Grouped pytz timezones

pretty_timezones.py

"""
Result:

TIMEZONE_CHOICES = [
    ("Africa", [
        ("Africa/Abidjan", "Abidjan"),
        ("Africa/Accra", "Accra"),
        #...
    ]),
    ("America", [
        ("America/Argentina/Buenos_Aires", "Argentina, Buenos Aires"),
        #...
    ]),
    #...
]


In django:

class User(models.Model):

    timezone = models.CharField(_("time zone"), max_length=32, choices=TIMEZONE_CHOICES, default='UTC')


html output:

<select id="id_timezone" name="timezone">
<optgroup label="Africa">
<option value="Africa/Abidjan">Abidjan</option>
<option value="Africa/Accra">Accra</option>
...
"""

import pytz


TIMEZONE_CHOICES = []


def _populate_timezone():
    timezones_tree = {}

    for tz in pytz.common_timezones:
        zone_parts = tz.split(u"/")
        zone = zone_parts[0]
        zone_list = timezones_tree.get(zone, [])

        if not zone_list:
            TIMEZONE_CHOICES.append((zone, zone_list))

        if len(zone_parts) > 1:
            zone_label = u", ".join(zone_parts[1:]).replace(u"_", u" ")
        else:
            zone_label = zone

        zone_list.append((tz, zone_label))
        timezones_tree[zone] = zone_list

_populate_timezone()