FM / pytz

/usr/lib/python3.6/site-packages/pytz

Name	Size	Mode	Actions
__pycache__/	-	0755	rm
exceptions.py	1333	0644	edit dl rm
lazy.py	5263	0644	edit dl rm
reference.py	3649	0644	edit dl rm
tzfile.py	4892	0644	edit dl rm
tzinfo.py	19368	0644	edit dl rm
__init__.py	14389	0644	edit dl rm

Edit: /usr/lib/python3.6/site-packages/pytz/tzfile.py (4892B)

#! /usr/libexec/platform-python
'''
$Id: tzfile.py,v 1.8 2004/06/03 00:15:24 zenzen Exp $
'''

try:
    from cStringIO import StringIO
except ImportError:
    from io import StringIO
from datetime import datetime, timedelta
from struct import unpack, calcsize

from pytz.tzinfo import StaticTzInfo, DstTzInfo, memorized_ttinfo
from pytz.tzinfo import memorized_datetime, memorized_timedelta

def _byte_string(s):
    """Cast a string or byte string to an ASCII byte string."""
    return s.encode('ASCII')

_NULL = _byte_string('\0')

def _std_string(s):
    """Cast a string or byte string to an ASCII string."""
    return str(s.decode('ASCII'))

def build_tzinfo(zone, fp):
    head_fmt = '>4s c 15x 6l'
    head_size = calcsize(head_fmt)
    (magic, format, ttisgmtcnt, ttisstdcnt,leapcnt, timecnt,
        typecnt, charcnt) =  unpack(head_fmt, fp.read(head_size))

# Make sure it is a tzfile(5) file
    assert magic == _byte_string('TZif'), 'Got magic %s' % repr(magic)

# Read out the transition times, localtime indices and ttinfo structures.
    data_fmt = '>%(timecnt)dl %(timecnt)dB %(ttinfo)s %(charcnt)ds' % dict(
        timecnt=timecnt, ttinfo='lBB'*typecnt, charcnt=charcnt)
    data_size = calcsize(data_fmt)
    data = unpack(data_fmt, fp.read(data_size))

# make sure we unpacked the right number of values
    assert len(data) == 2 * timecnt + 3 * typecnt + 1
    transitions = [memorized_datetime(trans)
                   for trans in data[:timecnt]]
    lindexes = list(data[timecnt:2 * timecnt])
    ttinfo_raw = data[2 * timecnt:-1]
    tznames_raw = data[-1]
    del data

# Process ttinfo into separate structs
    ttinfo = []
    tznames = {}
    i = 0
    while i < len(ttinfo_raw):
        # have we looked up this timezone name yet?
        tzname_offset = ttinfo_raw[i+2]
        if tzname_offset not in tznames:
            nul = tznames_raw.find(_NULL, tzname_offset)
            if nul < 0:
                nul = len(tznames_raw)
            tznames[tzname_offset] = _std_string(
                tznames_raw[tzname_offset:nul])
        ttinfo.append((ttinfo_raw[i],
                       bool(ttinfo_raw[i+1]),
                       tznames[tzname_offset]))
        i += 3

# Now build the timezone object
    if len(ttinfo) ==1 or len(transitions) == 0:
        ttinfo[0][0], ttinfo[0][2]
        cls = type(zone, (StaticTzInfo,), dict(
            zone=zone,
            _utcoffset=memorized_timedelta(ttinfo[0][0]),
            _tzname=ttinfo[0][2]))
    else:
        # Early dates use the first standard time ttinfo
        i = 0
        while ttinfo[i][1]:
            i += 1
        if ttinfo[i] == ttinfo[lindexes[0]]:
            transitions[0] = datetime.min
        else:
            transitions.insert(0, datetime.min)
            lindexes.insert(0, i)

# calculate transition info
        transition_info = []
        for i in range(len(transitions)):
            inf = ttinfo[lindexes[i]]
            utcoffset = inf[0]
            if not inf[1]:
                dst = 0
            else:
                for j in range(i-1, -1, -1):
                    prev_inf = ttinfo[lindexes[j]]
                    if not prev_inf[1]:
                        break
                dst = inf[0] - prev_inf[0] # dst offset

# Bad dst? Look further. DST > 24 hours happens when
                # a timzone has moved across the international dateline.
                if dst <= 0 or dst > 3600*3:
                    for j in range(i+1, len(transitions)):
                        stdinf = ttinfo[lindexes[j]]
                        if not stdinf[1]:
                            dst = inf[0] - stdinf[0]
                            if dst > 0:
                                break # Found a useful std time.

tzname = inf[2]

# Round utcoffset and dst to the nearest minute or the
            # datetime library will complain. Conversions to these timezones
            # might be up to plus or minus 30 seconds out, but it is
            # the best we can do.
            utcoffset = int((utcoffset + 30) // 60) * 60
            dst = int((dst + 30) // 60) * 60
            transition_info.append(memorized_ttinfo(utcoffset, dst, tzname))

cls = type(zone, (DstTzInfo,), dict(
            zone=zone,
            _utc_transition_times=transitions,
            _transition_info=transition_info))

return cls()

if __name__ == '__main__':
    import os.path
    from pprint import pprint
    base = os.path.join(os.path.dirname(__file__), 'zoneinfo')
    tz = build_tzinfo('Australia/Melbourne',
                      open(os.path.join(base,'Australia','Melbourne'), 'rb'))
    tz = build_tzinfo('US/Eastern',
                      open(os.path.join(base,'US','Eastern'), 'rb'))
    pprint(tz._utc_transition_times)
    #print tz.asPython(4)
    #print tz.transitions_mapping

cmd: