python - 在 Python/Django 中从城市获取时区

Question

使用 pytz，我能够像这样获得时区列表:

>>> from pytz import country_timezones
>>> print(' '.join(country_timezones('ch')))
Europe/Zurich
>>> print(' '.join(country_timezones('CH')))
Europe/Zurich

鉴于我从用户那里获得了国家和城市字段，我该如何确定城市的时区？

Answer 1

pytz 是 IANA 时区数据库(Olson 数据库)的包装器。它不包含将世界上任意城市映射到它所在时区的数据。

您可能需要一个地理编码器，例如 geopy可以使用各种网络服务将地点(例如城市名称)转换为其坐标(纬度、经度):

from geopy import geocoders # pip install geopy

g = geocoders.GoogleV3()
place, (lat, lng) = g.geocode('Singapore')
# -> (u'Singapore', (1.352083, 103.819836))

给定城市的纬度、经度，可以使用 tz_world, an efele.net/tz map / a shapefile of the TZ timezones of the world 找到它的时区例如，通过 postgis timezone db或 pytzwhere :

import tzwhere

w = tzwhere()
print w.tzNameAt(1.352083, 103.819836)
# -> Asia/Singapore

还有允许将(纬度、经度)转换为时区的网络服务，例如 askgeo , geonames , 请参阅 Timezone lookup from latitude longitude .

作为@dashesy pointed out in the comment , geopy 也可以找到时区(自 1.2 起):

timezone = g.timezone((lat, lng)) # return pytz timezone object
# -> <DstTzInfo 'Asia/Singapore' LMT+6:55:00 STD>

GeoNames also provides offline data允许直接从其名称获取城市的时区，例如:

#!/usr/bin/env python
import os
from collections import defaultdict
from datetime import datetime
from urllib   import urlretrieve
from urlparse import urljoin
from zipfile  import ZipFile

import pytz # pip install pytz

geonames_url = 'http://download.geonames.org/export/dump/'
basename = 'cities15000' # all cities with a population > 15000 or capitals
filename = basename + '.zip'

# get file
if not os.path.exists(filename):
    urlretrieve(urljoin(geonames_url, filename), filename)

# parse it
city2tz = defaultdict(set)
with ZipFile(filename) as zf, zf.open(basename + '.txt') as file:
    for line in file:
        fields = line.split(b'\t')
        if fields: # geoname table http://download.geonames.org/export/dump/
            name, asciiname, alternatenames = fields[1:4]
            timezone = fields[-2].decode('utf-8').strip()
            if timezone:
                for city in [name, asciiname] + alternatenames.split(b','):
                    city = city.decode('utf-8').strip()
                    if city:
                        city2tz[city].add(timezone)

print("Number of available city names (with aliases): %d" % len(city2tz))

#
n = sum((len(timezones) > 1) for city, timezones in city2tz.iteritems())
print("")
print("Find number of ambigious city names\n "
      "(that have more than one associated timezone): %d" % n)

#
fmt = '%Y-%m-%d %H:%M:%S %Z%z'
city = "Zurich"
for tzname in city2tz[city]:
    now = datetime.now(pytz.timezone(tzname))
    print("")
    print("%s is in %s timezone" % (city, tzname))
    print("Current time in %s is %s" % (city, now.strftime(fmt)))

输出

Number of available city names (with aliases): 112682

Find number of ambigious city names
 (that have more than one associated timezone): 2318

Zurich is in Europe/Zurich timezone
Current time in Zurich is 2013-05-13 11:36:33 CEST+0200