关于datetime：使用时区Python打印正确的时间

Printing correct time using timezones, Python

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好的，我们今天没有过好日子。

当您将正确的tzinfo对象附加到日期时间实例，然后strftime()它，它仍然以UTC格式出现，似乎忽略了我附加到它的漂亮的tzinfo对象。

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# python 2.5.4
now = datetime.now()
print now.strftime("%a %b %d %X" ) # %X is"locale's appropriate time rep"

pst = now.replace( tzinfo=Pacific )
print pst.strftime("%a %b %d %X" )

我们得到：

1 2	Mon Jan 18 17:30:16 Mon Jan 18 17:30:16

我发现如果我添加％z，我可以添加它应该计算的差异：

1 2	Mon Jan 18 17:32:38 Mon Jan 18 17:32:38 -0800

它只是在那里加-8，好像在说，"你自己做，foo。"

但是我希望strftime()能够简单地给我一个具有预定时间的字符串。

当我strftime()时，如何让strftime()为我做小时减法数学呢？

我正在使用的完整代码如下。

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from datetime import tzinfo, timedelta, datetime

ZERO = timedelta(0)
HOUR = timedelta(hours=1)

# A UTC class.

class UTC(tzinfo):
"""UTC"""
def utcoffset(self, dt):
return ZERO
def tzname(self, dt):
return"UTC"
def dst(self, dt):
return ZERO

utc = UTC()

# A class building tzinfo objects for fixed-offset time zones.
# Note that FixedOffset(0,"UTC") is a different way to build a
# UTC tzinfo object.
class FixedOffset(tzinfo):
"""Fixed offset in minutes east from UTC."""

def __init__(self, offset, name):
self.__offset = timedelta(minutes = offset)
self.__name = name

def utcoffset(self, dt):
return self.__offset

def tzname(self, dt):
return self.__name

def dst(self, dt):
return ZERO

# A class capturing the platform's idea of local time.

import time as _time

STDOFFSET = timedelta(seconds = -_time.timezone)
if _time.daylight:
DSTOFFSET = timedelta(seconds = -_time.altzone)
else:
DSTOFFSET = STDOFFSET

DSTDIFF = DSTOFFSET - STDOFFSET

class LocalTimezone(tzinfo):
def utcoffset(self, dt):
if self._isdst(dt):
return DSTOFFSET
else:
return STDOFFSET

def dst(self, dt):
if self._isdst(dt):
return DSTDIFF
else:
return ZERO

def tzname(self, dt):
return _time.tzname[self._isdst(dt)]

def _isdst(self, dt):
tt = (dt.year, dt.month, dt.day,
dt.hour, dt.minute, dt.second,
dt.weekday(), 0, -1)
stamp = _time.mktime(tt)
tt = _time.localtime(stamp)
return tt.tm_isdst > 0

Local = LocalTimezone()

# A complete implementation of current DST rules for major US time zones.

def first_sunday_on_or_after(dt):
days_to_go = 6 - dt.weekday()
if days_to_go:
dt += timedelta(days_to_go)
return dt

# In the US, DST starts at 2am (standard time) on the first Sunday in April.
DSTSTART = datetime(1, 4, 1, 2)
# and ends at 2am (DST time; 1am standard time) on the last Sunday of Oct.
# which is the first Sunday on or after Oct 25.
DSTEND = datetime(1, 10, 25, 1)

class USTimeZone(tzinfo):
def __init__(self, hours, reprname, stdname, dstname):
self.stdoffset = timedelta(hours=hours)
self.reprname = reprname
self.stdname = stdname
self.dstname = dstname

def __repr__(self):
return self.reprname

def tzname(self, dt):
if self.dst(dt):
return self.dstname
else:
return self.stdname

def utcoffset(self, dt):
return self.stdoffset + self.dst(dt)

def dst(self, dt):
if dt is None or dt.tzinfo is None:
# An exception may be sensible here, in one or both cases.
# It depends on how you want to treat them. The default
# fromutc() implementation (called by the default astimezone()
# implementation) passes a datetime with dt.tzinfo is self.
return ZERO
assert dt.tzinfo is self

# Find first Sunday in April & the last in October.
start = first_sunday_on_or_after(DSTSTART.replace(year=dt.year))
end = first_sunday_on_or_after(DSTEND.replace(year=dt.year))

# Can't compare naive to aware objects, so strip the timezone from
# dt first.
if start <= dt.replace(tzinfo=None) < end:
return HOUR
else:
return ZERO

Eastern = USTimeZone(-5,"Eastern", "EST","EDT")
#Central = USTimeZone(-6,"Central", "CST","CDT")
#Mountain = USTimeZone(-7,"Mountain","MST","MDT")
Pacific = USTimeZone(-8,"Pacific", "PST","PDT")

now = datetime.now()
print now.strftime("%a %b %d %X %z" )

pst = now.replace( tzinfo=Pacific )
print pst.strftime("%a %b %d %X %z" )