即使使用Dateutil解析器，Python 2.7 Datetime对象的偏移也无法察觉

Question

18 tz = pytz.timezone('America/Chicago')
19 TZOFFSETS = {'CST' : -21600}
20 POSTS_SINCE_HOUR = 1 
21 now_date = datetime.datetime.now(tz)
22 time_stamp = now_date - datetime.timedelta(hours=POSTS_SINCE_HOUR)
23 
24 thread_batch = []
25 for thread in threads:
26     last_post_time =  parse(
27             thread["LatestPostDate"],
28             tzinfos=TZOFFSETS)
29             
30     if last_post_time > time_stamp:
31         thread_batch.append(thread)


one@chat-dash ~/.willie $ python req.py 
Traceback (most recent call last):
  File "req.py", line 30, in <module>
    if last_post_time > time_stamp:
TypeError: can't compare offset-naive and offset-aware datetimes

I don't understand why it is complaining about this. I used datutil.parser parse to make last_post_time offset-aware.

Answer 1

The tzinfos parameter to parse does not specify which timezone to use, it merely allows you to add new custom time zones to the ones that dateutil recognizes. To get a timezone in the resulting datetime, the string passed to parse must include a timezone string.

If your string doesn't include a time zone, you need to add the timezone yourself after the datetime is returned.

Answer 2

更新：我最终无视parse（），使用datetime strptime，然后使用localize（）添加时区。