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cpython/Lib/zoneinfo/_zoneinfo.py

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import bisect
import calendar
import collections
import functools
import re
import weakref
from datetime import datetime, timedelta, tzinfo
from . import _common, _tzpath
EPOCH = datetime(1970, 1, 1)
EPOCHORDINAL = datetime(1970, 1, 1).toordinal()
# It is relatively expensive to construct new timedelta objects, and in most
# cases we're looking at the same deltas, like integer numbers of hours, etc.
# To improve speed and memory use, we'll keep a dictionary with references
# to the ones we've already used so far.
#
# Loading every time zone in the 2020a version of the time zone database
# requires 447 timedeltas, which requires approximately the amount of space
# that ZoneInfo("America/New_York") with 236 transitions takes up, so we will
# set the cache size to 512 so that in the common case we always get cache
# hits, but specifically crafted ZoneInfo objects don't leak arbitrary amounts
# of memory.
@functools.lru_cache(maxsize=512)
def _load_timedelta(seconds):
return timedelta(seconds=seconds)
class ZoneInfo(tzinfo):
_strong_cache_size = 8
_strong_cache = collections.OrderedDict()
_weak_cache = weakref.WeakValueDictionary()
__module__ = "zoneinfo"
def __init_subclass__(cls):
cls._strong_cache = collections.OrderedDict()
cls._weak_cache = weakref.WeakValueDictionary()
def __new__(cls, key):
instance = cls._weak_cache.get(key, None)
if instance is None:
instance = cls._weak_cache.setdefault(key, cls._new_instance(key))
instance._from_cache = True
# Update the "strong" cache
cls._strong_cache[key] = cls._strong_cache.pop(key, instance)
if len(cls._strong_cache) > cls._strong_cache_size:
cls._strong_cache.popitem(last=False)
return instance
@classmethod
def no_cache(cls, key):
obj = cls._new_instance(key)
obj._from_cache = False
return obj
@classmethod
def _new_instance(cls, key):
obj = super().__new__(cls)
obj._key = key
obj._file_path = obj._find_tzfile(key)
if obj._file_path is not None:
file_obj = open(obj._file_path, "rb")
else:
file_obj = _common.load_tzdata(key)
with file_obj as f:
obj._load_file(f)
return obj
@classmethod
def from_file(cls, fobj, /, key=None):
obj = super().__new__(cls)
obj._key = key
obj._file_path = None
obj._load_file(fobj)
obj._file_repr = repr(fobj)
# Disable pickling for objects created from files
obj.__reduce__ = obj._file_reduce
return obj
@classmethod
def clear_cache(cls, *, only_keys=None):
if only_keys is not None:
for key in only_keys:
cls._weak_cache.pop(key, None)
cls._strong_cache.pop(key, None)
else:
cls._weak_cache.clear()
cls._strong_cache.clear()
@property
def key(self):
return self._key
def utcoffset(self, dt):
return self._find_trans(dt).utcoff
def dst(self, dt):
return self._find_trans(dt).dstoff
def tzname(self, dt):
return self._find_trans(dt).tzname
def fromutc(self, dt):
"""Convert from datetime in UTC to datetime in local time"""
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")
timestamp = self._get_local_timestamp(dt)
num_trans = len(self._trans_utc)
if num_trans >= 1 and timestamp < self._trans_utc[0]:
tti = self._tti_before
fold = 0
elif (
num_trans == 0 or timestamp > self._trans_utc[-1]
) and not isinstance(self._tz_after, _ttinfo):
tti, fold = self._tz_after.get_trans_info_fromutc(
timestamp, dt.year
)
elif num_trans == 0:
tti = self._tz_after
fold = 0
else:
idx = bisect.bisect_right(self._trans_utc, timestamp)
if num_trans > 1 and timestamp >= self._trans_utc[1]:
tti_prev, tti = self._ttinfos[idx - 2 : idx]
elif timestamp > self._trans_utc[-1]:
tti_prev = self._ttinfos[-1]
tti = self._tz_after
else:
tti_prev = self._tti_before
tti = self._ttinfos[0]
# Detect fold
shift = tti_prev.utcoff - tti.utcoff
fold = shift.total_seconds() > timestamp - self._trans_utc[idx - 1]
dt += tti.utcoff
if fold:
return dt.replace(fold=1)
else:
return dt
def _find_trans(self, dt):
if dt is None:
if self._fixed_offset:
return self._tz_after
else:
return _NO_TTINFO
ts = self._get_local_timestamp(dt)
lt = self._trans_local[dt.fold]
num_trans = len(lt)
if num_trans and ts < lt[0]:
return self._tti_before
elif not num_trans or ts > lt[-1]:
if isinstance(self._tz_after, _TZStr):
return self._tz_after.get_trans_info(ts, dt.year, dt.fold)
else:
return self._tz_after
else:
# idx is the transition that occurs after this timestamp, so we
# subtract off 1 to get the current ttinfo
idx = bisect.bisect_right(lt, ts) - 1
assert idx >= 0
return self._ttinfos[idx]
def _get_local_timestamp(self, dt):
return (
(dt.toordinal() - EPOCHORDINAL) * 86400
+ dt.hour * 3600
+ dt.minute * 60
+ dt.second
)
def __str__(self):
if self._key is not None:
return f"{self._key}"
else:
return repr(self)
def __repr__(self):
if self._key is not None:
return f"{self.__class__.__name__}(key={self._key!r})"
else:
return f"{self.__class__.__name__}.from_file({self._file_repr})"
def __reduce__(self):
return (self.__class__._unpickle, (self._key, self._from_cache))
def _file_reduce(self):
import pickle
raise pickle.PicklingError(
"Cannot pickle a ZoneInfo file created from a file stream."
)
@classmethod
def _unpickle(cls, key, from_cache, /):
if from_cache:
return cls(key)
else:
return cls.no_cache(key)
def _find_tzfile(self, key):
return _tzpath.find_tzfile(key)
def _load_file(self, fobj):
# Retrieve all the data as it exists in the zoneinfo file
trans_idx, trans_utc, utcoff, isdst, abbr, tz_str = _common.load_data(
fobj
)
# Infer the DST offsets (needed for .dst()) from the data
dstoff = self._utcoff_to_dstoff(trans_idx, utcoff, isdst)
# Convert all the transition times (UTC) into "seconds since 1970-01-01 local time"
trans_local = self._ts_to_local(trans_idx, trans_utc, utcoff)
# Construct `_ttinfo` objects for each transition in the file
_ttinfo_list = [
_ttinfo(
_load_timedelta(utcoffset), _load_timedelta(dstoffset), tzname
)
for utcoffset, dstoffset, tzname in zip(utcoff, dstoff, abbr)
]
self._trans_utc = trans_utc
self._trans_local = trans_local
self._ttinfos = [_ttinfo_list[idx] for idx in trans_idx]
# Find the first non-DST transition
for i in range(len(isdst)):
if not isdst[i]:
self._tti_before = _ttinfo_list[i]
break
else:
if self._ttinfos:
self._tti_before = self._ttinfos[0]
else:
self._tti_before = None
# Set the "fallback" time zone
if tz_str is not None and tz_str != b"":
self._tz_after = _parse_tz_str(tz_str.decode())
else:
if not self._ttinfos and not _ttinfo_list:
raise ValueError("No time zone information found.")
if self._ttinfos:
self._tz_after = self._ttinfos[-1]
else:
self._tz_after = _ttinfo_list[-1]
# Determine if this is a "fixed offset" zone, meaning that the output
# of the utcoffset, dst and tzname functions does not depend on the
# specific datetime passed.
#
# We make three simplifying assumptions here:
#
# 1. If _tz_after is not a _ttinfo, it has transitions that might
# actually occur (it is possible to construct TZ strings that
# specify STD and DST but no transitions ever occur, such as
# AAA0BBB,0/0,J365/25).
# 2. If _ttinfo_list contains more than one _ttinfo object, the objects
# represent different offsets.
# 3. _ttinfo_list contains no unused _ttinfos (in which case an
# otherwise fixed-offset zone with extra _ttinfos defined may
# appear to *not* be a fixed offset zone).
#
# Violations to these assumptions would be fairly exotic, and exotic
# zones should almost certainly not be used with datetime.time (the
# only thing that would be affected by this).
if len(_ttinfo_list) > 1 or not isinstance(self._tz_after, _ttinfo):
self._fixed_offset = False
elif not _ttinfo_list:
self._fixed_offset = True
else:
self._fixed_offset = _ttinfo_list[0] == self._tz_after
@staticmethod
def _utcoff_to_dstoff(trans_idx, utcoffsets, isdsts):
# Now we must transform our ttis and abbrs into `_ttinfo` objects,
# but there is an issue: .dst() must return a timedelta with the
# difference between utcoffset() and the "standard" offset, but
# the "base offset" and "DST offset" are not encoded in the file;
# we can infer what they are from the isdst flag, but it is not
# sufficient to just look at the last standard offset, because
# occasionally countries will shift both DST offset and base offset.
typecnt = len(isdsts)
dstoffs = [0] * typecnt # Provisionally assign all to 0.
dst_cnt = sum(isdsts)
dst_found = 0
for i in range(1, len(trans_idx)):
if dst_cnt == dst_found:
break
idx = trans_idx[i]
dst = isdsts[idx]
# We're only going to look at daylight saving time
if not dst:
continue
# Skip any offsets that have already been assigned
if dstoffs[idx] != 0:
continue
dstoff = 0
utcoff = utcoffsets[idx]
comp_idx = trans_idx[i - 1]
if not isdsts[comp_idx]:
dstoff = utcoff - utcoffsets[comp_idx]
if not dstoff and idx < (typecnt - 1):
comp_idx = trans_idx[i + 1]
# If the following transition is also DST and we couldn't
# find the DST offset by this point, we're going to have to
# skip it and hope this transition gets assigned later
if isdsts[comp_idx]:
continue
dstoff = utcoff - utcoffsets[comp_idx]
if dstoff:
dst_found += 1
dstoffs[idx] = dstoff
else:
# If we didn't find a valid value for a given index, we'll end up
# with dstoff = 0 for something where `isdst=1`. This is obviously
# wrong - one hour will be a much better guess than 0
for idx in range(typecnt):
if not dstoffs[idx] and isdsts[idx]:
dstoffs[idx] = 3600
return dstoffs
@staticmethod
def _ts_to_local(trans_idx, trans_list_utc, utcoffsets):
"""Generate number of seconds since 1970 *in the local time*.
This is necessary to easily find the transition times in local time"""
if not trans_list_utc:
return [[], []]
# Start with the timestamps and modify in-place
trans_list_wall = [list(trans_list_utc), list(trans_list_utc)]
if len(utcoffsets) > 1:
offset_0 = utcoffsets[0]
offset_1 = utcoffsets[trans_idx[0]]
if offset_1 > offset_0:
offset_1, offset_0 = offset_0, offset_1
else:
offset_0 = offset_1 = utcoffsets[0]
trans_list_wall[0][0] += offset_0
trans_list_wall[1][0] += offset_1
for i in range(1, len(trans_idx)):
offset_0 = utcoffsets[trans_idx[i - 1]]
offset_1 = utcoffsets[trans_idx[i]]
if offset_1 > offset_0:
offset_1, offset_0 = offset_0, offset_1
trans_list_wall[0][i] += offset_0
trans_list_wall[1][i] += offset_1
return trans_list_wall
class _ttinfo:
__slots__ = ["utcoff", "dstoff", "tzname"]
def __init__(self, utcoff, dstoff, tzname):
self.utcoff = utcoff
self.dstoff = dstoff
self.tzname = tzname
def __eq__(self, other):
return (
self.utcoff == other.utcoff
and self.dstoff == other.dstoff
and self.tzname == other.tzname
)
def __repr__(self): # pragma: nocover
return (
f"{self.__class__.__name__}"
+ f"({self.utcoff}, {self.dstoff}, {self.tzname})"
)
_NO_TTINFO = _ttinfo(None, None, None)
class _TZStr:
__slots__ = (
"std",
"dst",
"start",
"end",
"get_trans_info",
"get_trans_info_fromutc",
"dst_diff",
)
def __init__(
self, std_abbr, std_offset, dst_abbr, dst_offset, start=None, end=None
):
self.dst_diff = dst_offset - std_offset
std_offset = _load_timedelta(std_offset)
self.std = _ttinfo(
utcoff=std_offset, dstoff=_load_timedelta(0), tzname=std_abbr
)
self.start = start
self.end = end
dst_offset = _load_timedelta(dst_offset)
delta = _load_timedelta(self.dst_diff)
self.dst = _ttinfo(utcoff=dst_offset, dstoff=delta, tzname=dst_abbr)
# These are assertions because the constructor should only be called
# by functions that would fail before passing start or end
assert start is not None, "No transition start specified"
assert end is not None, "No transition end specified"
self.get_trans_info = self._get_trans_info
self.get_trans_info_fromutc = self._get_trans_info_fromutc
def transitions(self, year):
start = self.start.year_to_epoch(year)
end = self.end.year_to_epoch(year)
return start, end
def _get_trans_info(self, ts, year, fold):
"""Get the information about the current transition - tti"""
start, end = self.transitions(year)
# With fold = 0, the period (denominated in local time) with the
# smaller offset starts at the end of the gap and ends at the end of
# the fold; with fold = 1, it runs from the start of the gap to the
# beginning of the fold.
#
# So in order to determine the DST boundaries we need to know both
# the fold and whether DST is positive or negative (rare), and it
# turns out that this boils down to fold XOR is_positive.
if fold == (self.dst_diff >= 0):
end -= self.dst_diff
else:
start += self.dst_diff
if start < end:
isdst = start <= ts < end
else:
isdst = not (end <= ts < start)
return self.dst if isdst else self.std
def _get_trans_info_fromutc(self, ts, year):
start, end = self.transitions(year)
start -= self.std.utcoff.total_seconds()
end -= self.dst.utcoff.total_seconds()
if start < end:
isdst = start <= ts < end
else:
isdst = not (end <= ts < start)
# For positive DST, the ambiguous period is one dst_diff after the end
# of DST; for negative DST, the ambiguous period is one dst_diff before
# the start of DST.
if self.dst_diff > 0:
ambig_start = end
ambig_end = end + self.dst_diff
else:
ambig_start = start
ambig_end = start - self.dst_diff
fold = ambig_start <= ts < ambig_end
return (self.dst if isdst else self.std, fold)
def _post_epoch_days_before_year(year):
"""Get the number of days between 1970-01-01 and YEAR-01-01"""
y = year - 1
return y * 365 + y // 4 - y // 100 + y // 400 - EPOCHORDINAL
class _DayOffset:
__slots__ = ["d", "julian", "hour", "minute", "second"]
def __init__(self, d, julian, hour=2, minute=0, second=0):
min_day = 0 + julian # convert bool to int
if not min_day <= d <= 365:
raise ValueError(f"d must be in [{min_day}, 365], not: {d}")
self.d = d
self.julian = julian
self.hour = hour
self.minute = minute
self.second = second
def year_to_epoch(self, year):
days_before_year = _post_epoch_days_before_year(year)
d = self.d
if self.julian and d >= 59 and calendar.isleap(year):
d += 1
epoch = (days_before_year + d) * 86400
epoch += self.hour * 3600 + self.minute * 60 + self.second
return epoch
class _CalendarOffset:
__slots__ = ["m", "w", "d", "hour", "minute", "second"]
_DAYS_BEFORE_MONTH = (
-1,
0,
31,
59,
90,
120,
151,
181,
212,
243,
273,
304,
334,
)
def __init__(self, m, w, d, hour=2, minute=0, second=0):
if not 1 <= m <= 12:
raise ValueError("m must be in [1, 12]")
if not 1 <= w <= 5:
raise ValueError("w must be in [1, 5]")
if not 0 <= d <= 6:
raise ValueError("d must be in [0, 6]")
self.m = m
self.w = w
self.d = d
self.hour = hour
self.minute = minute
self.second = second
@classmethod
def _ymd2ord(cls, year, month, day):
return (
_post_epoch_days_before_year(year)
+ cls._DAYS_BEFORE_MONTH[month]
+ (month > 2 and calendar.isleap(year))
+ day
)
# TODO: These are not actually epoch dates as they are expressed in local time
def year_to_epoch(self, year):
"""Calculates the datetime of the occurrence from the year"""
# We know year and month, we need to convert w, d into day of month
#
# Week 1 is the first week in which day `d` (where 0 = Sunday) appears.
# Week 5 represents the last occurrence of day `d`, so we need to know
# the range of the month.
first_day, days_in_month = calendar.monthrange(year, self.m)
# This equation seems magical, so I'll break it down:
# 1. calendar says 0 = Monday, POSIX says 0 = Sunday
# so we need first_day + 1 to get 1 = Monday -> 7 = Sunday,
# which is still equivalent because this math is mod 7
# 2. Get first day - desired day mod 7: -1 % 7 = 6, so we don't need
# to do anything to adjust negative numbers.
# 3. Add 1 because month days are a 1-based index.
month_day = (self.d - (first_day + 1)) % 7 + 1
# Now use a 0-based index version of `w` to calculate the w-th
# occurrence of `d`
month_day += (self.w - 1) * 7
# month_day will only be > days_in_month if w was 5, and `w` means
# "last occurrence of `d`", so now we just check if we over-shot the
# end of the month and if so knock off 1 week.
if month_day > days_in_month:
month_day -= 7
ordinal = self._ymd2ord(year, self.m, month_day)
epoch = ordinal * 86400
epoch += self.hour * 3600 + self.minute * 60 + self.second
return epoch
def _parse_tz_str(tz_str):
# The tz string has the format:
#
# std[offset[dst[offset],start[/time],end[/time]]]
#
# std and dst must be 3 or more characters long and must not contain
# a leading colon, embedded digits, commas, nor a plus or minus signs;
# The spaces between "std" and "offset" are only for display and are
# not actually present in the string.
#
# The format of the offset is ``[+|-]hh[:mm[:ss]]``
offset_str, *start_end_str = tz_str.split(",", 1)
parser_re = re.compile(
r"""
(?P<std>[^<0-9:.+-]+|<[a-zA-Z0-9+-]+>)
(?:
(?P<stdoff>[+-]?\d{1,3}(?::\d{2}(?::\d{2})?)?)
(?:
(?P<dst>[^0-9:.+-]+|<[a-zA-Z0-9+-]+>)
(?P<dstoff>[+-]?\d{1,3}(?::\d{2}(?::\d{2})?)?)?
)? # dst
)? # stdoff
""",
re.ASCII|re.VERBOSE
)
m = parser_re.fullmatch(offset_str)
if m is None:
raise ValueError(f"{tz_str} is not a valid TZ string")
std_abbr = m.group("std")
dst_abbr = m.group("dst")
dst_offset = None
std_abbr = std_abbr.strip("<>")
if dst_abbr:
dst_abbr = dst_abbr.strip("<>")
if std_offset := m.group("stdoff"):
try:
std_offset = _parse_tz_delta(std_offset)
except ValueError as e:
raise ValueError(f"Invalid STD offset in {tz_str}") from e
else:
std_offset = 0
if dst_abbr is not None:
if dst_offset := m.group("dstoff"):
try:
dst_offset = _parse_tz_delta(dst_offset)
except ValueError as e:
raise ValueError(f"Invalid DST offset in {tz_str}") from e
else:
dst_offset = std_offset + 3600
if not start_end_str:
raise ValueError(f"Missing transition rules: {tz_str}")
start_end_strs = start_end_str[0].split(",", 1)
try:
start, end = (_parse_dst_start_end(x) for x in start_end_strs)
except ValueError as e:
raise ValueError(f"Invalid TZ string: {tz_str}") from e
return _TZStr(std_abbr, std_offset, dst_abbr, dst_offset, start, end)
elif start_end_str:
raise ValueError(f"Transition rule present without DST: {tz_str}")
else:
# This is a static ttinfo, don't return _TZStr
return _ttinfo(
_load_timedelta(std_offset), _load_timedelta(0), std_abbr
)
def _parse_dst_start_end(dststr):
date, *time = dststr.split("/", 1)
type = date[:1]
if type == "M":
n_is_julian = False
m = re.fullmatch(r"M(\d{1,2})\.(\d).(\d)", date, re.ASCII)
if m is None:
raise ValueError(f"Invalid dst start/end date: {dststr}")
date_offset = tuple(map(int, m.groups()))
offset = _CalendarOffset(*date_offset)
else:
if type == "J":
n_is_julian = True
date = date[1:]
else:
n_is_julian = False
doy = int(date)
offset = _DayOffset(doy, n_is_julian)
if time:
offset.hour, offset.minute, offset.second = _parse_transition_time(time[0])
return offset
def _parse_transition_time(time_str):
match = re.fullmatch(
r"(?P<sign>[+-])?(?P<h>\d{1,3})(:(?P<m>\d{2})(:(?P<s>\d{2}))?)?",
time_str,
re.ASCII
)
if match is None:
raise ValueError(f"Invalid time: {time_str}")
h, m, s = (int(v or 0) for v in match.group("h", "m", "s"))
if h > 167:
raise ValueError(
f"Hour must be in [0, 167]: {time_str}"
)
if match.group("sign") == "-":
h, m, s = -h, -m, -s
return h, m, s
def _parse_tz_delta(tz_delta):
match = re.fullmatch(
r"(?P<sign>[+-])?(?P<h>\d{1,3})(:(?P<m>\d{2})(:(?P<s>\d{2}))?)?",
tz_delta,
re.ASCII
)
# Anything passed to this function should already have hit an equivalent
# regular expression to find the section to parse.
assert match is not None, tz_delta
h, m, s = (int(v or 0) for v in match.group("h", "m", "s"))
total = h * 3600 + m * 60 + s
if h > 24:
raise ValueError(
f"Offset hours must be in [0, 24]: {tz_delta}"
)
# Yes, +5 maps to an offset of -5h
if match.group("sign") != "-":
total = -total
return total
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