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[3.7] bpo-30699: Improve example on datetime tzinfo instances (GH-4290) #13811

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miss-islington merged 1 commit into from
Jun 4, 2019
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[3.7] bpo-30699: Improve example on datetime tzinfo instances (GH-4290) #13811

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111 changes: 60 additions & 51 deletions Doc/library/datetime.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -1348,56 +1348,64 @@ Examples of working with datetime objects:

Using datetime with tzinfo:

>>> from datetime import timedelta, datetime, tzinfo
>>> class GMT1(tzinfo):
>>> from datetime import timedelta, datetime, tzinfo, timezone
>>> class KabulTz(tzinfo):
... # Kabul used +4 until 1945, when they moved to +4:30
... UTC_MOVE_DATE = datetime(1944, 12, 31, 20, tzinfo=timezone.utc)
... def utcoffset(self, dt):
... return timedelta(hours=1) + self.dst(dt)
... def dst(self, dt):
... # DST starts last Sunday in March
... d = datetime(dt.year, 4, 1) # ends last Sunday in October
... self.dston = d - timedelta(days=d.weekday() + 1)
... d = datetime(dt.year, 11, 1)
... self.dstoff = d - timedelta(days=d.weekday() + 1)
... if self.dston <= dt.replace(tzinfo=None) < self.dstoff:
... return timedelta(hours=1)
... if dt.year < 1945:
... return timedelta(hours=4)
... elif (1945, 1, 1, 0, 0) <= dt.timetuple()[:5] < (1945, 1, 1, 0, 30):
... # If dt falls in the imaginary range, use fold to decide how
... # to resolve. See PEP495
... return timedelta(hours=4, minutes=(30 if dt.fold else 0))
... else:
... return timedelta(0)
... def tzname(self,dt):
... return "GMT +1"
... return timedelta(hours=4, minutes=30)
...
... def fromutc(self, dt):
... # A custom implementation is required for fromutc as
... # the input to this function is a datetime with utc values
... # but with a tzinfo set to self
... # See datetime.astimezone or fromtimestamp
...
... # Follow same validations as in datetime.tzinfo
... if not isinstance(dt, datetime):
... raise TypeError("fromutc() requires a datetime argument")
... if dt.tzinfo is not self:
... raise ValueError("dt.tzinfo is not self")
...
... if dt.replace(tzinfo=timezone.utc) >= self.UTC_MOVE_DATE:
... return dt + timedelta(hours=4, minutes=30)
... else:
... return dt + timedelta(hours=4)
...
>>> class GMT2(tzinfo):
... def utcoffset(self, dt):
... return timedelta(hours=2) + self.dst(dt)
... def dst(self, dt):
... d = datetime(dt.year, 4, 1)
... self.dston = d - timedelta(days=d.weekday() + 1)
... d = datetime(dt.year, 11, 1)
... self.dstoff = d - timedelta(days=d.weekday() + 1)
... if self.dston <= dt.replace(tzinfo=None) < self.dstoff:
... return timedelta(hours=1)
... return timedelta(0)
...
... def tzname(self, dt):
... if dt >= self.UTC_MOVE_DATE:
... return "+04:30"
... else:
... return timedelta(0)
... def tzname(self,dt):
... return "GMT +2"
... return "+04"
...
>>> gmt1 = GMT1()
>>> # Daylight Saving Time
>>> dt1 = datetime(2006, 11, 21, 16, 30, tzinfo=gmt1)
>>> dt1.dst()
datetime.timedelta(0)
>>> dt1.utcoffset()
datetime.timedelta(seconds=3600)
>>> dt2 = datetime(2006, 6, 14, 13, 0, tzinfo=gmt1)
>>> dt2.dst()
datetime.timedelta(seconds=3600)
>>> dt2.utcoffset()
datetime.timedelta(seconds=7200)
... def __repr__(self):
... return f"{self.__class__.__name__}()"
...
>>> tz1 = KabulTz()
>>> # Datetime before the change
>>> dt1 = datetime(1900, 11, 21, 16, 30, tzinfo=tz1)
>>> print(dt1.utcoffset())
4:00:00
>>> # Datetime after the change
>>> dt2 = datetime(2006, 6, 14, 13, 0, tzinfo=tz1)
>>> print(dt2.utcoffset())
4:30:00
>>> # Convert datetime to another time zone
>>> dt3 = dt2.astimezone(GMT2())
>>> dt3 # doctest: +ELLIPSIS
datetime.datetime(2006, 6, 14, 14, 0, tzinfo=<GMT2 object at 0x...>)
>>> dt2 # doctest: +ELLIPSIS
datetime.datetime(2006, 6, 14, 13, 0, tzinfo=<GMT1 object at 0x...>)
>>> dt3 = dt2.astimezone(timezone.utc)
>>> dt3
datetime.datetime(2006, 6, 14, 8, 30, tzinfo=datetime.timezone.utc)
>>> dt2
datetime.datetime(2006, 6, 14, 13, 0, tzinfo=KabulTz())
>>> dt2.utctimetuple() == dt3.utctimetuple()
True

Expand Down Expand Up @@ -1639,26 +1647,27 @@ Instance methods:
Example:

>>> from datetime import time, tzinfo, timedelta
>>> class GMT1(tzinfo):
>>> class TZ1(tzinfo):
... def utcoffset(self, dt):
... return timedelta(hours=1)
... def dst(self, dt):
... return timedelta(0)
... def tzname(self,dt):
... return "Europe/Prague"
... return "+01:00"
... def __repr__(self):
... return f"{self.__class__.__name__}()"
...
>>> t = time(12, 10, 30, tzinfo=GMT1())
>>> t # doctest: +ELLIPSIS
datetime.time(12, 10, 30, tzinfo=<GMT1 object at 0x...>)
>>> gmt = GMT1()
>>> t = time(12, 10, 30, tzinfo=TZ1())
>>> t
datetime.time(12, 10, 30, tzinfo=TZ1())
>>> t.isoformat()
'12:10:30+01:00'
>>> t.dst()
datetime.timedelta(0)
>>> t.tzname()
'Europe/Prague'
'+01:00'
>>> t.strftime("%H:%M:%S %Z")
'12:10:30 Europe/Prague'
'12:10:30 +01:00'
>>> 'The {} is {:%H:%M}.'.format("time", t)
'The time is 12:10.'

Expand Down