Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.11/site-packages/pytz/tzinfo.py: 29%

1'''Base classes and helpers for building zone specific tzinfo classes'''

3from datetime import datetime, timedelta, tzinfo

4from bisect import bisect_right

5try:

6 set

7except NameError:

8 from sets import Set as set

10import pytz

11from pytz.exceptions import AmbiguousTimeError, NonExistentTimeError

13__all__ = []

15_timedelta_cache = {}

18def memorized_timedelta(seconds):

19 '''Create only one instance of each distinct timedelta'''

20 try:

21 return _timedelta_cache[seconds]

22 except KeyError:

23 delta = timedelta(seconds=seconds)

24 _timedelta_cache[seconds] = delta

25 return delta

28_epoch = datetime(1970, 1, 1, 0, 0) # datetime.utcfromtimestamp(0)

29_datetime_cache = {0: _epoch}

32def memorized_datetime(seconds):

33 '''Create only one instance of each distinct datetime'''

34 try:

35 return _datetime_cache[seconds]

36 except KeyError:

37 # NB. We can't just do datetime.fromtimestamp(seconds, tz=timezone.utc).replace(tzinfo=None)

38 # as this fails with negative values under Windows (Bug #90096)

39 dt = _epoch + timedelta(seconds=seconds)

40 _datetime_cache[seconds] = dt

41 return dt

44_ttinfo_cache = {}

47def memorized_ttinfo(*args):

48 '''Create only one instance of each distinct tuple'''

49 try:

50 return _ttinfo_cache[args]

51 except KeyError:

52 ttinfo = (

53 memorized_timedelta(args[0]),

54 memorized_timedelta(args[1]),

55 args[2]

56 )

57 _ttinfo_cache[args] = ttinfo

58 return ttinfo

61_notime = memorized_timedelta(0)

64def _to_seconds(td):

65 '''Convert a timedelta to seconds'''

66 return td.seconds + td.days * 24 * 60 * 60

69class BaseTzInfo(tzinfo):

70 # Overridden in subclass

71 _utcoffset = None

72 _tzname = None

73 zone = None

75 def __str__(self):

76 return self.zone

79class StaticTzInfo(BaseTzInfo):

80 '''A timezone that has a constant offset from UTC

82 These timezones are rare, as most locations have changed their

83 offset at some point in their history

84 '''

85 def fromutc(self, dt):

86 '''See datetime.tzinfo.fromutc'''

87 if dt.tzinfo is not None and dt.tzinfo is not self:

88 raise ValueError('fromutc: dt.tzinfo is not self')

89 return (dt + self._utcoffset).replace(tzinfo=self)

91 def utcoffset(self, dt, is_dst=None):

92 '''See datetime.tzinfo.utcoffset

94 is_dst is ignored for StaticTzInfo, and exists only to

95 retain compatibility with DstTzInfo.

96 '''

97 return self._utcoffset

99 def dst(self, dt, is_dst=None):

100 '''See datetime.tzinfo.dst

101

102 is_dst is ignored for StaticTzInfo, and exists only to

103 retain compatibility with DstTzInfo.

104 '''

105 return _notime

106

107 def tzname(self, dt, is_dst=None):

108 '''See datetime.tzinfo.tzname

109

110 is_dst is ignored for StaticTzInfo, and exists only to

111 retain compatibility with DstTzInfo.

112 '''

113 return self._tzname

114

115 def localize(self, dt, is_dst=False):

116 '''Convert naive time to local time'''

117 if dt.tzinfo is not None:

118 raise ValueError('Not naive datetime (tzinfo is already set)')

119 return dt.replace(tzinfo=self)

120

121 def normalize(self, dt, is_dst=False):

122 '''Correct the timezone information on the given datetime.

123

124 This is normally a no-op, as StaticTzInfo timezones never have

125 ambiguous cases to correct:

126

127 >>> from pytz import timezone

128 >>> gmt = timezone('GMT')

129 >>> isinstance(gmt, StaticTzInfo)

130 True

131 >>> dt = datetime(2011, 5, 8, 1, 2, 3, tzinfo=gmt)

132 >>> gmt.normalize(dt) is dt

133 True

134

135 The supported method of converting between timezones is to use

136 datetime.astimezone(). Currently normalize() also works:

137

138 >>> la = timezone('America/Los_Angeles')

139 >>> dt = la.localize(datetime(2011, 5, 7, 1, 2, 3))

140 >>> fmt = '%Y-%m-%d %H:%M:%S %Z (%z)'

141 >>> gmt.normalize(dt).strftime(fmt)

142 '2011-05-07 08:02:03 GMT (+0000)'

143 '''

144 if dt.tzinfo is self:

145 return dt

146 if dt.tzinfo is None:

147 raise ValueError('Naive time - no tzinfo set')

148 return dt.astimezone(self)

149

150 def __repr__(self):

151 return '<StaticTzInfo %r>' % (self.zone,)

152

153 def __reduce__(self):

154 # Special pickle to zone remains a singleton and to cope with

155 # database changes.

156 return pytz._p, (self.zone,)

157

158

159class DstTzInfo(BaseTzInfo):

160 '''A timezone that has a variable offset from UTC

161

162 The offset might change if daylight saving time comes into effect,

163 or at a point in history when the region decides to change their

164 timezone definition.

165 '''

166 # Overridden in subclass

167

168 # Sorted list of DST transition times, UTC

169 _utc_transition_times = None

170

171 # [(utcoffset, dstoffset, tzname)] corresponding to

172 # _utc_transition_times entries

173 _transition_info = None

174

175 zone = None

176

177 # Set in __init__

178

179 _tzinfos = None

180 _dst = None # DST offset

181

182 def __init__(self, _inf=None, _tzinfos=None):

183 if _inf:

184 self._tzinfos = _tzinfos

185 self._utcoffset, self._dst, self._tzname = _inf

186 else:

187 _tzinfos = {}

188 self._tzinfos = _tzinfos

189 self._utcoffset, self._dst, self._tzname = (

190 self._transition_info[0])

191 _tzinfos[self._transition_info[0]] = self

192 for inf in self._transition_info[1:]:

193 if inf not in _tzinfos:

194 _tzinfos[inf] = self.__class__(inf, _tzinfos)

195

196 def fromutc(self, dt):

197 '''See datetime.tzinfo.fromutc'''

198 if (dt.tzinfo is not None and

199 getattr(dt.tzinfo, '_tzinfos', None) is not self._tzinfos):

200 raise ValueError('fromutc: dt.tzinfo is not self')

201 dt = dt.replace(tzinfo=None)

202 idx = max(0, bisect_right(self._utc_transition_times, dt) - 1)

203 inf = self._transition_info[idx]

204 return (dt + inf[0]).replace(tzinfo=self._tzinfos[inf])

205

206 def normalize(self, dt):

207 '''Correct the timezone information on the given datetime

208

209 If date arithmetic crosses DST boundaries, the tzinfo

210 is not magically adjusted. This method normalizes the

211 tzinfo to the correct one.

212

213 To test, first we need to do some setup

214

215 >>> from pytz import timezone

216 >>> utc = timezone('UTC')

217 >>> eastern = timezone('US/Eastern')

218 >>> fmt = '%Y-%m-%d %H:%M:%S %Z (%z)'

219

220 We next create a datetime right on an end-of-DST transition point,

221 the instant when the wallclocks are wound back one hour.

222

223 >>> utc_dt = datetime(2002, 10, 27, 6, 0, 0, tzinfo=utc)

224 >>> loc_dt = utc_dt.astimezone(eastern)

225 >>> loc_dt.strftime(fmt)

226 '2002-10-27 01:00:00 EST (-0500)'

227

228 Now, if we subtract a few minutes from it, note that the timezone

229 information has not changed.

230

231 >>> before = loc_dt - timedelta(minutes=10)

232 >>> before.strftime(fmt)

233 '2002-10-27 00:50:00 EST (-0500)'

234

235 But we can fix that by calling the normalize method

236

237 >>> before = eastern.normalize(before)

238 >>> before.strftime(fmt)

239 '2002-10-27 01:50:00 EDT (-0400)'

240

241 The supported method of converting between timezones is to use

242 datetime.astimezone(). Currently, normalize() also works:

243

244 >>> th = timezone('Asia/Bangkok')

245 >>> am = timezone('Europe/Amsterdam')

246 >>> dt = th.localize(datetime(2011, 5, 7, 1, 2, 3))

247 >>> fmt = '%Y-%m-%d %H:%M:%S %Z (%z)'

248 >>> am.normalize(dt).strftime(fmt)

249 '2011-05-06 20:02:03 CEST (+0200)'

250 '''

251 if dt.tzinfo is None:

252 raise ValueError('Naive time - no tzinfo set')

253

254 # Convert dt in localtime to UTC

255 offset = dt.tzinfo._utcoffset

256 dt = dt.replace(tzinfo=None)

257 dt = dt - offset

258 # convert it back, and return it

259 return self.fromutc(dt)

260

261 def localize(self, dt, is_dst=False):

262 '''Convert naive time to local time.

263

264 This method should be used to construct localtimes, rather

265 than passing a tzinfo argument to a datetime constructor.

266

267 is_dst is used to determine the correct timezone in the ambigous

268 period at the end of daylight saving time.

269

270 >>> from pytz import timezone

271 >>> fmt = '%Y-%m-%d %H:%M:%S %Z (%z)'

272 >>> amdam = timezone('Europe/Amsterdam')

273 >>> dt = datetime(2004, 10, 31, 2, 0, 0)

274 >>> loc_dt1 = amdam.localize(dt, is_dst=True)

275 >>> loc_dt2 = amdam.localize(dt, is_dst=False)

276 >>> loc_dt1.strftime(fmt)

277 '2004-10-31 02:00:00 CEST (+0200)'

278 >>> loc_dt2.strftime(fmt)

279 '2004-10-31 02:00:00 CET (+0100)'

280 >>> str(loc_dt2 - loc_dt1)

281 '1:00:00'

282

283 Use is_dst=None to raise an AmbiguousTimeError for ambiguous

284 times at the end of daylight saving time

285

286 >>> try:

287 ... loc_dt1 = amdam.localize(dt, is_dst=None)

288 ... except AmbiguousTimeError:

289 ... print('Ambiguous')

290 Ambiguous

291

292 is_dst defaults to False

293

294 >>> amdam.localize(dt) == amdam.localize(dt, False)

295 True

296

297 is_dst is also used to determine the correct timezone in the

298 wallclock times jumped over at the start of daylight saving time.

299

300 >>> pacific = timezone('US/Pacific')

301 >>> dt = datetime(2008, 3, 9, 2, 0, 0)

302 >>> ploc_dt1 = pacific.localize(dt, is_dst=True)

303 >>> ploc_dt2 = pacific.localize(dt, is_dst=False)

304 >>> ploc_dt1.strftime(fmt)

305 '2008-03-09 02:00:00 PDT (-0700)'

306 >>> ploc_dt2.strftime(fmt)

307 '2008-03-09 02:00:00 PST (-0800)'

308 >>> str(ploc_dt2 - ploc_dt1)

309 '1:00:00'

310

311 Use is_dst=None to raise a NonExistentTimeError for these skipped

312 times.

313

314 >>> try:

315 ... loc_dt1 = pacific.localize(dt, is_dst=None)

316 ... except NonExistentTimeError:

317 ... print('Non-existent')

318 Non-existent

319 '''

320 if dt.tzinfo is not None:

321 raise ValueError('Not naive datetime (tzinfo is already set)')

322

323 # Find the two best possibilities.

324 possible_loc_dt = set()

325 for delta in [timedelta(days=-1), timedelta(days=1)]:

326 try:

327 loc_dt = dt + delta

328 except OverflowError:

329 # dt is close to datetime.min or datetime.max; skip this

330 # direction rather than raising an OverflowError to the caller.

331 continue

332 idx = max(0, bisect_right(

333 self._utc_transition_times, loc_dt) - 1)

334 inf = self._transition_info[idx]

335 tzinfo = self._tzinfos[inf]

336 loc_dt = tzinfo.normalize(dt.replace(tzinfo=tzinfo))

337 if loc_dt.replace(tzinfo=None) == dt:

338 possible_loc_dt.add(loc_dt)

339

340 if len(possible_loc_dt) == 1:

341 return possible_loc_dt.pop()

342

343 # If there are no possibly correct timezones, we are attempting

344 # to convert a time that never happened - the time period jumped

345 # during the start-of-DST transition period.

346 if len(possible_loc_dt) == 0:

347 # If we refuse to guess, raise an exception.

348 if is_dst is None:

349 raise NonExistentTimeError(dt)

350

351 # If we are forcing the pre-DST side of the DST transition, we

352 # obtain the correct timezone by winding the clock forward a few

353 # hours.

354 elif is_dst:

355 return self.localize(

356 dt + timedelta(hours=6), is_dst=True) - timedelta(hours=6)

357

358 # If we are forcing the post-DST side of the DST transition, we

359 # obtain the correct timezone by winding the clock back.

360 else:

361 return self.localize(

362 dt - timedelta(hours=6),

363 is_dst=False) + timedelta(hours=6)

364

365 # If we get this far, we have multiple possible timezones - this

366 # is an ambiguous case occurring during the end-of-DST transition.

367

368 # If told to be strict, raise an exception since we have an

369 # ambiguous case

370 if is_dst is None:

371 raise AmbiguousTimeError(dt)

372

373 # Filter out the possiblilities that don't match the requested

374 # is_dst

375 filtered_possible_loc_dt = [

376 p for p in possible_loc_dt if bool(p.tzinfo._dst) == is_dst

377 ]

378

379 # Hopefully we only have one possibility left. Return it.

380 if len(filtered_possible_loc_dt) == 1:

381 return filtered_possible_loc_dt[0]

382

383 if len(filtered_possible_loc_dt) == 0:

384 filtered_possible_loc_dt = list(possible_loc_dt)

385

386 # If we get this far, we have in a wierd timezone transition

387 # where the clocks have been wound back but is_dst is the same

388 # in both (eg. Europe/Warsaw 1915 when they switched to CET).

389 # At this point, we just have to guess unless we allow more

390 # hints to be passed in (such as the UTC offset or abbreviation),

391 # but that is just getting silly.

392 #

393 # Choose the earliest (by UTC) applicable timezone if is_dst=True

394 # Choose the latest (by UTC) applicable timezone if is_dst=False

395 # i.e., behave like end-of-DST transition

396 dates = {} # utc -> local

397 for local_dt in filtered_possible_loc_dt:

398 utc_time = (

399 local_dt.replace(tzinfo=None) - local_dt.tzinfo._utcoffset)

400 assert utc_time not in dates

401 dates[utc_time] = local_dt

402 return dates[[min, max][not is_dst](dates)]

403

404 def utcoffset(self, dt, is_dst=None):

405 '''See datetime.tzinfo.utcoffset

406

407 The is_dst parameter may be used to remove ambiguity during DST

408 transitions.

409

410 >>> from pytz import timezone

411 >>> tz = timezone('America/St_Johns')

412 >>> ambiguous = datetime(2009, 10, 31, 23, 30)

413

414 >>> str(tz.utcoffset(ambiguous, is_dst=False))

415 '-1 day, 20:30:00'

416

417 >>> str(tz.utcoffset(ambiguous, is_dst=True))

418 '-1 day, 21:30:00'

419

420 >>> try:

421 ... tz.utcoffset(ambiguous)

422 ... except AmbiguousTimeError:

423 ... print('Ambiguous')

424 Ambiguous

425

426 '''

427 if dt is None:

428 return None

429 elif dt.tzinfo is not self:

430 dt = self.localize(dt, is_dst)

431 return dt.tzinfo._utcoffset

432 else:

433 return self._utcoffset

434

435 def dst(self, dt, is_dst=None):

436 '''See datetime.tzinfo.dst

437

438 The is_dst parameter may be used to remove ambiguity during DST

439 transitions.

440

441 >>> from pytz import timezone

442 >>> tz = timezone('America/St_Johns')

443

444 >>> normal = datetime(2009, 9, 1)

445

446 >>> str(tz.dst(normal))

447 '1:00:00'

448 >>> str(tz.dst(normal, is_dst=False))

449 '1:00:00'

450 >>> str(tz.dst(normal, is_dst=True))

451 '1:00:00'

452

453 >>> ambiguous = datetime(2009, 10, 31, 23, 30)

454

455 >>> str(tz.dst(ambiguous, is_dst=False))

456 '0:00:00'

457 >>> str(tz.dst(ambiguous, is_dst=True))

458 '1:00:00'

459 >>> try:

460 ... tz.dst(ambiguous)

461 ... except AmbiguousTimeError:

462 ... print('Ambiguous')

463 Ambiguous

464

465 '''

466 if dt is None:

467 return None

468 elif dt.tzinfo is not self:

469 dt = self.localize(dt, is_dst)

470 return dt.tzinfo._dst

471 else:

472 return self._dst

473

474 def tzname(self, dt, is_dst=None):

475 '''See datetime.tzinfo.tzname

476

477 The is_dst parameter may be used to remove ambiguity during DST

478 transitions.

479

480 >>> from pytz import timezone

481 >>> tz = timezone('America/St_Johns')

482

483 >>> normal = datetime(2009, 9, 1)

484

485 >>> tz.tzname(normal)

486 'NDT'

487 >>> tz.tzname(normal, is_dst=False)

488 'NDT'

489 >>> tz.tzname(normal, is_dst=True)

490 'NDT'

491

492 >>> ambiguous = datetime(2009, 10, 31, 23, 30)

493

494 >>> tz.tzname(ambiguous, is_dst=False)

495 'NST'

496 >>> tz.tzname(ambiguous, is_dst=True)

497 'NDT'

498 >>> try:

499 ... tz.tzname(ambiguous)

500 ... except AmbiguousTimeError:

501 ... print('Ambiguous')

502 Ambiguous

503 '''

504 if dt is None:

505 return self.zone

506 elif dt.tzinfo is not self:

507 dt = self.localize(dt, is_dst)

508 return dt.tzinfo._tzname

509 else:

510 return self._tzname

511

512 def __repr__(self):

513 if self._dst:

514 dst = 'DST'

515 else:

516 dst = 'STD'

517 if self._utcoffset > _notime:

518 return '<DstTzInfo %r %s+%s %s>' % (

519 self.zone, self._tzname, self._utcoffset, dst

520 )

521 else:

522 return '<DstTzInfo %r %s%s %s>' % (

523 self.zone, self._tzname, self._utcoffset, dst

524 )

525

526 def __reduce__(self):

527 # Special pickle to zone remains a singleton and to cope with

528 # database changes.

529 return pytz._p, (

530 self.zone,

531 _to_seconds(self._utcoffset),

532 _to_seconds(self._dst),

533 self._tzname

534 )

535

536

537def unpickler(zone, utcoffset=None, dstoffset=None, tzname=None):

538 """Factory function for unpickling pytz tzinfo instances.

539

540 This is shared for both StaticTzInfo and DstTzInfo instances, because

541 database changes could cause a zones implementation to switch between

542 these two base classes and we can't break pickles on a pytz version

543 upgrade.

544 """

545 # Raises a KeyError if zone no longer exists, which should never happen

546 # and would be a bug.

547 tz = pytz.timezone(zone)

548

549 # A StaticTzInfo - just return it

550 if utcoffset is None:

551 return tz

552

553 # This pickle was created from a DstTzInfo. We need to

554 # determine which of the list of tzinfo instances for this zone

555 # to use in order to restore the state of any datetime instances using

556 # it correctly.

557 utcoffset = memorized_timedelta(utcoffset)

558 dstoffset = memorized_timedelta(dstoffset)

559 try:

560 return tz._tzinfos[(utcoffset, dstoffset, tzname)]

561 except KeyError:

562 # The particular state requested in this timezone no longer exists.

563 # This indicates a corrupt pickle, or the timezone database has been

564 # corrected violently enough to make this particular

565 # (utcoffset,dstoffset) no longer exist in the zone, or the

566 # abbreviation has been changed.

567 pass

568

569 # See if we can find an entry differing only by tzname. Abbreviations

570 # get changed from the initial guess by the database maintainers to

571 # match reality when this information is discovered.

572 for localized_tz in tz._tzinfos.values():

573 if (localized_tz._utcoffset == utcoffset and

574 localized_tz._dst == dstoffset):

575 return localized_tz

576

577 # This (utcoffset, dstoffset) information has been removed from the

578 # zone. Add it back. This might occur when the database maintainers have

579 # corrected incorrect information. datetime instances using this

580 # incorrect information will continue to do so, exactly as they were

581 # before being pickled. This is purely an overly paranoid safety net - I

582 # doubt this will ever been needed in real life.

583 inf = (utcoffset, dstoffset, tzname)

584 tz._tzinfos[inf] = tz.__class__(inf, tz._tzinfos)

585 return tz._tzinfos[inf]