Lib/tzparse.py

   1 """Parse a timezone specification."""
   2
   3 # XXX Unfinished.
   4 # XXX Only the typical form "XXXhhYYY;ddd/hh,ddd/hh" is currently supported.
   5
   6 tzpat = ('^([A-Z][A-Z][A-Z])([-+]?[0-9]+)([A-Z][A-Z][A-Z]);'
   7           '([0-9]+)/([0-9]+),([0-9]+)/([0-9]+)$')
   8
   9 tzprog = None
  10
  11 def tzparse(tzstr):
  12         """Given a timezone spec, return a tuple of information
  13         (tzname, delta, dstname, daystart, hourstart, dayend, hourend),
  14         where 'tzname' is the name of the timezone, 'delta' is the offset
  15         in hours from GMT, 'dstname' is the name of the daylight-saving
  16         timezone, and 'daystart'/'hourstart' and 'dayend'/'hourend'
  17         specify the starting and ending points for daylight saving time."""
  18         global tzprog
  19         if tzprog == None:
  20                 import re
  21                 tzprog = re.compile(tzpat)
  22         match = tzprog.match(tzstr)
  23         if not match:
  24                 raise ValueError, 'not the TZ syntax I understand'
  25         subs = []
  26         for i in range(1, 8):
  27                 subs.append(match.group(i))
  28         for i in (1, 3, 4, 5, 6):
  29                 subs[i] = eval(subs[i])
  30         [tzname, delta, dstname, daystart, hourstart, dayend, hourend] = subs
  31         return (tzname, delta, dstname, daystart, hourstart, dayend, hourend)
  32
  33 def tzlocaltime(secs, params):
  34         """Given a Unix time in seconds and a tuple of information about
  35         a timezone as returned by tzparse(), return the local time in the
  36         form (year, month, day, hour, min, sec, yday, wday, tzname)."""
  37         import time
  38         (tzname, delta, dstname, daystart, hourstart, dayend, hourend) = params
  39         year, month, days, hours, mins, secs, yday, wday, isdst = \
  40                 time.gmtime(secs - delta*3600)
  41         if (daystart, hourstart) <= (yday+1, hours) < (dayend, hourend):
  42                 tzname = dstname
  43                 hours = hours + 1
  44         return year, month, days, hours, mins, secs, yday, wday, tzname
  45
  46 def tzset():
  47         """Determine the current timezone from the "TZ" environment variable."""
  48         global tzparams, timezone, altzone, daylight, tzname
  49         import os
  50         tzstr = os.environ['TZ']
  51         tzparams = tzparse(tzstr)
  52         timezone = tzparams[1] * 3600
  53         altzone = timezone - 3600
  54         daylight = 1
  55         tzname = tzparams[0], tzparams[2]
  56
  57 def isdst(secs):
  58         """Return true if daylight-saving time is in effect for the given
  59         Unix time in the current timezone."""
  60         import time
  61         (tzname, delta, dstname, daystart, hourstart, dayend, hourend) = \
  62                 tzparams
  63         year, month, days, hours, mins, secs, yday, wday, isdst = \
  64                 time.gmtime(secs - delta*3600)
  65         return (daystart, hourstart) <= (yday+1, hours) < (dayend, hourend)
  66
  67 tzset()
  68
  69 def localtime(secs):
  70         """Get the local time in the current timezone."""
  71         return tzlocaltime(secs, tzparams)
  72
  73 def test():
  74         from time import asctime, gmtime
  75         import time, sys
  76         now = time.time()
  77         x = localtime(now)
  78         tm = x[:-1] + (0,)
  79         print 'now =', now, '=', asctime(tm), x[-1]
  80         now = now - now % (24*3600)
  81         if sys.argv[1:]: now = now + eval(sys.argv[1])
  82         x = gmtime(now)
  83         tm = x[:-1] + (0,)
  84         print 'gmtime =', now, '=', asctime(tm), 'yday =', x[-2]
  85         jan1 = now - x[-2]*24*3600
  86         x = localtime(jan1)
  87         tm = x[:-1] + (0,)
  88         print 'jan1 =', jan1, '=', asctime(tm), x[-1]
  89         for d in range(85, 95) + range(265, 275):
  90                 t = jan1 + d*24*3600
  91                 x = localtime(t)
  92                 tm = x[:-1] + (0,)
  93                 print 'd =', d, 't =', t, '=', asctime(tm), x[-1]