Python 如何修改程序默认时区

os.environ['TZ'] = 'Asia/Shanghai'

import pytz
import datetime
tz = pytz.timezone('Asia/Shanghai')
datetime.datetime.now(tz)#获得此时区的当期那时间
#可以通过pytz.timezone('cn')获取中国的所有可用的时区
#['Asia/Shanghai', 'Asia/Harbin', 'Asia/Chongqing', 'Asia/Urumqi', 'Asia/Kashgar']

# 拿到UTC时间，并强制设置时区为UTC+0:00:
>>> utc_dt = datetime.utcnow().replace(tzinfo=timezone.utc)
>>> print(utc_dt)
2015-05-18 09:05:12.377316+00:00
# astimezone()将转换时区为北京时间:
>>> bj_dt = utc_dt.astimezone(timezone(timedelta(hours=8)))
>>> print(bj_dt)
2015-05-18 17:05:12.377316+08:00
# astimezone()将转换时区为东京时间:
>>> tokyo_dt = utc_dt.astimezone(timezone(timedelta(hours=9)))
>>> print(tokyo_dt)
2015-05-18 18:05:12.377316+09:00
# astimezone()将bj_dt转换时区为东京时间:
>>> tokyo_dt2 = bj_dt.astimezone(timezone(timedelta(hours=9)))
>>> print(tokyo_dt2)
2015-05-18 18:05:12.377316+09:00

utc_dt = datetime.utcnow()
bj_dt = utc_dt+timedelta(hours=8)
delta_dt = bj_dt - sql_dt