fixup! Backport zoneinfo logic into tzfile

dateutil/test/test_tz.py

@@ -2019,8 +2019,9 @@ def testFileStart1(self):
 
     def testFileEnd1(self):
         tzc = tz.tzfile(BytesIO(base64.b64decode(TZFILE_EST5EDT)))
-        self.assertEqual(datetime(2003, 10, 26, 0, 59, tzinfo=tzc).tzname(),
-                         "EDT")
+        self.assertEqual(
+            datetime(2003, 10, 26, 0, 59, tzinfo=tzc).tzname(), "EDT"
+        )
         end_est = tz.enfold(datetime(2003, 10, 26, 1, 0, tzinfo=tzc))
         self.assertEqual(end_est.tzname(), "EST")
 
@@ -2031,8 +2032,7 @@ def testFileLastTransition(self):
                          "EDT")
 
         last_date = tz.enfold(datetime(2037, 10, 25, 1, 0, tzinfo=tzc), fold=1)
-        self.assertEqual(last_date.tzname(),
-                         "EST")
+        self.assertEqual(last_date.tzname(), "EST")
 
         self.assertEqual(datetime(2038, 5, 25, 12, 0, tzinfo=tzc).tzname(),
                          "EST")

dateutil/tz/_tzfile.py

@@ -1,15 +1,15 @@
 import bisect
 import calendar
 import functools
+import re
 import struct
 import sys
-import re
 from datetime import datetime, timedelta
 
-from ._common import _tzinfo, tzname_in_python2, enfold
-
 import six
 
+from ._common import _tzinfo, enfold, tzname_in_python2
+
 EPOCH = datetime(1970, 1, 1)
 EPOCHORDINAL = EPOCH.toordinal()
 
@@ -24,6 +24,7 @@
     def _nullcontext(context):
         yield context
 
+
 # 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
@@ -37,8 +38,10 @@ def _nullcontext(context):
 # of memory.
 _TIMEDELTA_CACHE_SIZE = 512
 if six.PY2:
+
     def _cache_load_timedelta(f):
         from collections import OrderedDict
+
         from six.moves import _thread
 
         CACHE_LOCK = _thread.allocate_lock()
@@ -59,9 +62,12 @@ def cached_load_timedelta(seconds):
             return rv
 
         return cached_load_timedelta
+
+
 else:
     _cache_load_timedelta = functools.lru_cache(maxsize=512)
 
+
 @_cache_load_timedelta
 def _load_timedelta(seconds):
     return timedelta(seconds=seconds)
@@ -155,7 +161,7 @@ def __init__(self, fileobj, filename=None, key=None):
         file_opened_here = False
         if isinstance(fileobj, six.string_types):
             self._filename = fileobj
-            fileobj = open(fileobj, 'rb')
+            fileobj = open(fileobj, "rb")
             file_opened_here = True
         elif filename is not None:
             self._filename = filename
@@ -198,7 +204,9 @@ def _is_ambiguous_or_imaginary(self, dt):
         tti_1 = self._find_trans(dt, fold=1, timestamp=timestamp)
 
         # Returns 1 if ambiguous, -1 if imaginary and 0 otherwise.
-        return int(tti_0.utcoff > tti_1.utcoff) - int(tti_1.utcoff > tti_0.utcoff)
+        return int(tti_0.utcoff > tti_1.utcoff) - int(
+            tti_1.utcoff > tti_0.utcoff
+        )
 
     def utcoffset(self, dt):
         return self._find_trans(dt).utcoff
@@ -354,7 +362,6 @@ def _load_from_data(self, data):
             utcoff = [60 * ((s + 30) // 60) for s in utcoff]
             dstoff = [60 * ((s + 30) // 60) for s in dstoff]
 
-
         # 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)
 
@@ -519,14 +526,15 @@ def _ts_to_local(trans_idx, trans_list_utc, utcoffsets):
 
         return trans_list_wall
 
-
     def __eq__(self, other):
         if not isinstance(other, tzfile):
             return NotImplemented
 
-        return (self._trans_utc == other._trans_utc and
-                self._trans_local == other._trans_local and
-                self._ttinfos == other._ttinfos)
+        return (
+            self._trans_utc == other._trans_utc
+            and self._trans_local == other._trans_local
+            and self._ttinfos == other._ttinfos
+        )
 
     __hash__ = None
 
@@ -572,8 +580,7 @@ def load_data(fobj):
     # The data portion starts with timecnt transitions and indices
     if timecnt:
         trans_list_utc = struct.unpack(
-            ">%s%s" % (timecnt, time_type),
-            fobj.read(timecnt * time_size)
+            ">%s%s" % (timecnt, time_type), fobj.read(timecnt * time_size)
         )
         trans_idx = struct.unpack(">%sB" % timecnt, fobj.read(timecnt))
     else:
@@ -644,13 +651,13 @@ def get_abbr(idx):
 
 class _TZifHeader:
     __slots__ = [
-        'version',
-        'isutcnt',
-        'isstdcnt',
-        'leapcnt',
-        'timecnt',
-        'typecnt',
-        'charcnt',
+        "version",
+        "isutcnt",
+        "isstdcnt",
+        "leapcnt",
+        "timecnt",
+        "typecnt",
+        "charcnt",
     ]
 
     def __init__(self, *args):
@@ -661,11 +668,11 @@ def __init__(self, *args):
     @classmethod
     def from_file(cls, stream):
         # The header starts with a 4-byte "magic" value
-        if stream.read(4) != b'TZif':
-            raise ValueError('Invalid TZif file: magic not found')
+        if stream.read(4) != b"TZif":
+            raise ValueError("Invalid TZif file: magic not found")
 
         _version = stream.read(1)
-        if _version == b'\x00':
+        if _version == b"\x00":
             version = 1
         else:
             version = int(_version)
@@ -674,7 +681,7 @@ def from_file(cls, stream):
         args = (version,)
 
         # Slots are defined in the order that the bytes are arranged
-        args = args + struct.unpack('>6l', stream.read(24))
+        args = args + struct.unpack(">6l", stream.read(24))
 
         return cls(*args)
 
@@ -695,17 +702,22 @@ def __eq__(self, other):
         )
 
     def __repr__(self):  # pragma: nocover
-        return (
-            "%s(%s, %s, %s)" % (self.__class__.__name__, self.utcoff, self.dstoff, self.tzname,)
+        return "%s(%s, %s, %s)" % (
+            self.__class__.__name__,
+            self.utcoff,
+            self.dstoff,
+            self.tzname,
         )
 
 
 _NO_TTINFO = _ttinfo(None, None, None)
 
+
 def _unpack(t):
     # Python 2-specific backport for x, *y = t
     return t[0], t[1:]
 
+
 def _parse_tz_str(tz_str):
     # The tz string has the format:
     #
@@ -840,6 +852,7 @@ def _parse_tz_delta(tz_delta):
 
     return total
 
+
 class _TZStr:
     __slots__ = (
         "std",

dateutil/tz/tz.py

@@ -19,9 +19,15 @@
 import six
 from six import string_types
 from six.moves import _thread
-from ._common import tzname_in_python2, _tzinfo
-from ._common import tzrangebase, enfold
-from ._common import _validate_fromutc_inputs
+
+from ._common import (
+    _tzinfo,
+    _validate_fromutc_inputs,
+    enfold,
+    tzname_in_python2,
+    tzrangebase,
+)
+from ._factories import _TzOffsetFactory, _TzSingleton, _TzStrFactory
 from ._tzfile import tzfile
 
 from ._factories import _TzSingleton, _TzOffsetFactory