无法使用datetime python模块将带时区的datetime字符串转换为UTC的datetime

Question

我在将这种格式的日期时间字符串"%d %b %Y %X %Z"转换为"%Y-%m-%dT%X%z"时遇到问题。时区信息被剥离。例如:

>> import datetime
>> datetime_string_raw = "18 Nov 2022 08:57:04 EST" 
>> datetime_utc =  datetime.datetime.strptime(datetime_string_raw, "%d %b %Y %X %Z").strftime("%Y-%m-%dT%X%z")
>> print(datetime_utc)
2022-11-18T08:57:04

我怎么能让它打印UTC偏移量?为什么%Z和%Z没有任何作用?谢谢!

Answer 1

使用dateutil的解析器并定义缩写名应该与哪个时区相似:

import datetime
import dateutil # pip install python-dateutil
tzinfos = {"EST": dateutil.tz.gettz("America/New_York"),
"EDT": dateutil.tz.gettz("America/New_York")}
datetime_string_raw = "18 Nov 2022 08:57:04 EST" 
datetime_ny = dateutil.parser.parse(datetime_string_raw, tzinfos=tzinfos)
print(datetime_ny)
# 2022-11-18 08:57:04-05:00
datetime_utc = datetime_ny.astimezone(datetime.timezone.utc)
print(datetime_utc)
# 2022-11-18 13:57:04+00:00

---

您可以仅使用标准库完成基本相同的操作，但它需要对日期/时间字符串进行一些预处理。例:

import datetime
import zoneinfo # Python >= 3.9
def parse_dt_with_tz(dt_string: str, fmt: str, tzinfos: dict) -> datetime.datetime:
"""Parse date/time string with abbreviated time zone name to aware datetime."""
parts = dt_string.split(" ")
tz = tzinfos.get(parts[-1]) # last element is the tz name
if not tz:
raise ValueError(f"no entry found for {parts[-1]} in tzinfos")
return datetime.datetime.strptime(" ".join(parts[:-1]), fmt).replace(tzinfo=tz)
# usage
tzinfos = {"EST": zoneinfo.ZoneInfo("America/New_York"),
"EDT": zoneinfo.ZoneInfo("America/New_York")}
s = "18 Nov 2022 08:57:04 EST"
dt = parse_dt_with_tz(s, "%d %b %Y %H:%M:%S", tzinfos)
print(dt, repr(dt))
# 2022-11-18 08:57:04-05:00 datetime.datetime(2022, 11, 18, 8, 57, 4, tzinfo=zoneinfo.ZoneInfo(key='America/New_York'))