Closes issue #24773: Implement PEP 495 (Local Time Disambiguation).

Include/datetime.h

@@ -81,6 +81,7 @@ typedef struct
 typedef struct
 {
     _PyDateTime_TIMEHEAD
+    unsigned char fold;
     PyObject *tzinfo;
 } PyDateTime_Time;              /* hastzinfo true */
 
@@ -108,6 +109,7 @@ typedef struct
 typedef struct
 {
     _PyDateTime_DATETIMEHEAD
+    unsigned char fold;
     PyObject *tzinfo;
 } PyDateTime_DateTime;          /* hastzinfo true */
 
@@ -125,6 +127,7 @@ typedef struct
     ((((PyDateTime_DateTime*)o)->data[7] << 16) |       \
      (((PyDateTime_DateTime*)o)->data[8] << 8)  |       \
       ((PyDateTime_DateTime*)o)->data[9])
+#define PyDateTime_DATE_GET_FOLD(o)        (((PyDateTime_DateTime*)o)->fold)
 
 /* Apply for time instances. */
 #define PyDateTime_TIME_GET_HOUR(o)        (((PyDateTime_Time*)o)->data[0])
@@ -134,6 +137,7 @@ typedef struct
     ((((PyDateTime_Time*)o)->data[3] << 16) |           \
      (((PyDateTime_Time*)o)->data[4] << 8)  |           \
       ((PyDateTime_Time*)o)->data[5])
+#define PyDateTime_TIME_GET_FOLD(o)        (((PyDateTime_Time*)o)->fold)
 
 /* Apply for time delta instances */
 #define PyDateTime_DELTA_GET_DAYS(o)         (((PyDateTime_Delta*)o)->days)
@@ -162,6 +166,11 @@ typedef struct {
     PyObject *(*DateTime_FromTimestamp)(PyObject*, PyObject*, PyObject*);
     PyObject *(*Date_FromTimestamp)(PyObject*, PyObject*);
 
+    /* PEP 495 constructors */
+    PyObject *(*DateTime_FromDateAndTimeAndFold)(int, int, int, int, int, int, int,
+        PyObject*, int, PyTypeObject*);
+    PyObject *(*Time_FromTimeAndFold)(int, int, int, int, PyObject*, int, PyTypeObject*);
+
 } PyDateTime_CAPI;
 
 #define PyDateTime_CAPSULE_NAME "datetime.datetime_CAPI"
@@ -217,10 +226,18 @@ static PyDateTime_CAPI *PyDateTimeAPI = NULL;
     PyDateTimeAPI->DateTime_FromDateAndTime(year, month, day, hour, \
         min, sec, usec, Py_None, PyDateTimeAPI->DateTimeType)
 
+#define PyDateTime_FromDateAndTimeAndFold(year, month, day, hour, min, sec, usec, fold) \
+    PyDateTimeAPI->DateTime_FromDateAndTimeAndFold(year, month, day, hour, \
+        min, sec, usec, Py_None, fold, PyDateTimeAPI->DateTimeType)
+
 #define PyTime_FromTime(hour, minute, second, usecond) \
     PyDateTimeAPI->Time_FromTime(hour, minute, second, usecond, \
         Py_None, PyDateTimeAPI->TimeType)
 
+#define PyTime_FromTimeAndFold(hour, minute, second, usecond, fold) \
+    PyDateTimeAPI->Time_FromTimeAndFold(hour, minute, second, usecond, \
+        Py_None, fold, PyDateTimeAPI->TimeType)
+
 #define PyDelta_FromDSU(days, seconds, useconds) \
     PyDateTimeAPI->Delta_FromDelta(days, seconds, useconds, 1, \
         PyDateTimeAPI->DeltaType)

Lib/test/libregrtest/cmdline.py

@@ -112,6 +112,8 @@ resources to test.  Currently only the following are defined:
 
     gui -       Run tests that require a running GUI.
 
+    tzdata -    Run tests that require timezone data.
+
 To enable all resources except one, use '-uall,-<resource>'.  For
 example, to run all the tests except for the gui tests, give the
 option '-uall,-gui'.
@@ -119,7 +121,7 @@ option '-uall,-gui'.
 
 
 RESOURCE_NAMES = ('audio', 'curses', 'largefile', 'network',
-                  'decimal', 'cpu', 'subprocess', 'urlfetch', 'gui')
+                  'decimal', 'cpu', 'subprocess', 'urlfetch', 'gui', 'tzdata')
 
 class _ArgParser(argparse.ArgumentParser):
 

Misc/NEWS

@@ -26,6 +26,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #24773: Implemented PEP 495 (Local Time Disambiguation).
+
 - Expose the EPOLLEXCLUSIVE constant (when it is defined) in the select module.
 
 - Issue #27567: Expose the EPOLLRDHUP and POLLRDHUP constants in the select

Tools/tz/zdump.py

+import sys
+import os
+import struct
+from array import array
+from collections import namedtuple
+from datetime import datetime, timedelta
+
+ttinfo = namedtuple('ttinfo', ['tt_gmtoff', 'tt_isdst', 'tt_abbrind'])
+
+class TZInfo:
+    def __init__(self, transitions, type_indices, ttis, abbrs):
+        self.transitions = transitions
+        self.type_indices = type_indices
+        self.ttis = ttis
+        self.abbrs = abbrs
+
+    @classmethod
+    def fromfile(cls, fileobj):
+        if fileobj.read(4).decode() != "TZif":
+            raise ValueError("not a zoneinfo file")
+        fileobj.seek(20)
+        header = fileobj.read(24)
+        tzh = (tzh_ttisgmtcnt, tzh_ttisstdcnt, tzh_leapcnt,
+               tzh_timecnt, tzh_typecnt, tzh_charcnt) = struct.unpack(">6l", header)
+        transitions = array('i')
+        transitions.fromfile(fileobj, tzh_timecnt)
+        if sys.byteorder != 'big':
+            transitions.byteswap()
+
+        type_indices = array('B')
+        type_indices.fromfile(fileobj, tzh_timecnt)
+
+        ttis = []
+        for i in range(tzh_typecnt):
+            ttis.append(ttinfo._make(struct.unpack(">lbb", fileobj.read(6))))
+
+        abbrs = fileobj.read(tzh_charcnt)
+
+        self = cls(transitions, type_indices, ttis, abbrs)
+        self.tzh = tzh
+
+        return self
+
+    def dump(self, stream, start=None, end=None):
+        for j, (trans, i) in enumerate(zip(self.transitions, self.type_indices)):
+            utc = datetime.utcfromtimestamp(trans)
+            tti = self.ttis[i]
+            lmt = datetime.utcfromtimestamp(trans + tti.tt_gmtoff)
+            abbrind = tti.tt_abbrind
+            abbr = self.abbrs[abbrind:self.abbrs.find(0, abbrind)].decode()
+            if j > 0:
+                prev_tti = self.ttis[self.type_indices[j - 1]]
+                shift = " %+g" % ((tti.tt_gmtoff - prev_tti.tt_gmtoff) / 3600)
+            else:
+                shift = ''
+            print("%s UTC = %s %-5s isdst=%d" % (utc, lmt, abbr, tti[1]) + shift, file=stream)
+
+    @classmethod
+    def zonelist(cls, zonedir='/usr/share/zoneinfo'):
+        zones = []
+        for root, _, files in os.walk(zonedir):
+            for f in files:
+                p = os.path.join(root, f)
+                with open(p, 'rb') as o:
+                    magic =  o.read(4)
+                if magic == b'TZif':
+                    zones.append(p[len(zonedir) + 1:])
+        return zones
+
+if __name__ == '__main__':
+    if len(sys.argv) < 2:
+        zones = TZInfo.zonelist()
+        for z in zones:
+            print(z)
+        sys.exit()
+    filepath = sys.argv[1]
+    if not filepath.startswith('/'):
+        filepath = os.path.join('/usr/share/zoneinfo', filepath)
+    with open(filepath, 'rb') as fileobj:
+        tzi = TZInfo.fromfile(fileobj)
+    tzi.dump(sys.stdout)