Lib/_strptime.py

   1 """Strptime-related classes and functions.
   2
   3 CLASSES:
   4     LocaleTime -- Discovers and stores locale-specific time information
   5     TimeRE -- Creates regexes for pattern matching a string of text containing
   6                 time information
   7
   8 FUNCTIONS:
   9     _getlang -- Figure out what language is being used for the locale
  10     strptime -- Calculates the time struct represented by the passed-in string
  11
  12 """
  13 import time
  14 import locale
  15 import calendar
  16 from re import compile as re_compile
  17 from re import IGNORECASE
  18 from re import escape as re_escape
  19 from datetime import date as datetime_date
  20 try:
  21     from thread import allocate_lock as _thread_allocate_lock
  22 except:
  23     from dummy_thread import allocate_lock as _thread_allocate_lock
  24
  25 __author__ = "Brett Cannon"
  26 __email__ = "brett@python.org"
  27
  28 __all__ = ['strptime']
  29
  30 def _getlang():
  31     # Figure out what the current language is set to.
  32     return locale.getlocale(locale.LC_TIME)
  33
  34 class LocaleTime(object):
  35     """Stores and handles locale-specific information related to time.
  36
  37     ATTRIBUTES:
  38         f_weekday -- full weekday names (7-item list)
  39         a_weekday -- abbreviated weekday names (7-item list)
  40         f_month -- full month names (13-item list; dummy value in [0], which
  41                     is added by code)
  42         a_month -- abbreviated month names (13-item list, dummy value in
  43                     [0], which is added by code)
  44         am_pm -- AM/PM representation (2-item list)
  45         LC_date_time -- format string for date/time representation (string)
  46         LC_date -- format string for date representation (string)
  47         LC_time -- format string for time representation (string)
  48         timezone -- daylight- and non-daylight-savings timezone representation
  49                     (2-item list of sets)
  50         lang -- Language used by instance (2-item tuple)
  51     """
  52
  53     def __init__(self):
  54         """Set all attributes.
  55
  56         Order of methods called matters for dependency reasons.
  57
  58         The locale language is set at the offset and then checked again before
  59         exiting.  This is to make sure that the attributes were not set with a
  60         mix of information from more than one locale.  This would most likely
  61         happen when using threads where one thread calls a locale-dependent
  62         function while another thread changes the locale while the function in
  63         the other thread is still running.  Proper coding would call for
  64         locks to prevent changing the locale while locale-dependent code is
  65         running.  The check here is done in case someone does not think about
  66         doing this.
  67
  68         Only other possible issue is if someone changed the timezone and did
  69         not call tz.tzset .  That is an issue for the programmer, though,
  70         since changing the timezone is worthless without that call.
  71
  72         """
  73         self.lang = _getlang()
  74         self.__calc_weekday()
  75         self.__calc_month()
  76         self.__calc_am_pm()
  77         self.__calc_timezone()
  78         self.__calc_date_time()
  79         if _getlang() != self.lang:
  80             raise ValueError("locale changed during initialization")
  81
  82     def __pad(self, seq, front):
  83         # Add '' to seq to either the front (is True), else the back.
  84         seq = list(seq)
  85         if front:
  86             seq.insert(0, '')
  87         else:
  88             seq.append('')
  89         return seq
  90
  91     def __calc_weekday(self):
  92         # Set self.a_weekday and self.f_weekday using the calendar
  93         # module.
  94         a_weekday = [calendar.day_abbr[i].lower() for i in range(7)]
  95         f_weekday = [calendar.day_name[i].lower() for i in range(7)]
  96         self.a_weekday = a_weekday
  97         self.f_weekday = f_weekday
  98
  99     def __calc_month(self):
 100         # Set self.f_month and self.a_month using the calendar module.
 101         a_month = [calendar.month_abbr[i].lower() for i in range(13)]
 102         f_month = [calendar.month_name[i].lower() for i in range(13)]
 103         self.a_month = a_month
 104         self.f_month = f_month
 105
 106     def __calc_am_pm(self):
 107         # Set self.am_pm by using time.strftime().
 108
 109         # The magic date (1999,3,17,hour,44,55,2,76,0) is not really that
 110         # magical; just happened to have used it everywhere else where a
 111         # static date was needed.
 112         am_pm = []
 113         for hour in (01,22):
 114             time_tuple = time.struct_time((1999,3,17,hour,44,55,2,76,0))
 115             am_pm.append(time.strftime("%p", time_tuple).lower())
 116         self.am_pm = am_pm
 117
 118     def __calc_date_time(self):
 119         # Set self.date_time, self.date, & self.time by using
 120         # time.strftime().
 121
 122         # Use (1999,3,17,22,44,55,2,76,0) for magic date because the amount of
 123         # overloaded numbers is minimized.  The order in which searches for
 124         # values within the format string is very important; it eliminates
 125         # possible ambiguity for what something represents.
 126         time_tuple = time.struct_time((1999,3,17,22,44,55,2,76,0))
 127         date_time = [None, None, None]
 128         date_time[0] = time.strftime("%c", time_tuple).lower()
 129         date_time[1] = time.strftime("%x", time_tuple).lower()
 130         date_time[2] = time.strftime("%X", time_tuple).lower()
 131         replacement_pairs = [('%', '%%'), (self.f_weekday[2], '%A'),
 132                     (self.f_month[3], '%B'), (self.a_weekday[2], '%a'),
 133                     (self.a_month[3], '%b'), (self.am_pm[1], '%p'),
 134                     ('1999', '%Y'), ('99', '%y'), ('22', '%H'),
 135                     ('44', '%M'), ('55', '%S'), ('76', '%j'),
 136                     ('17', '%d'), ('03', '%m'), ('3', '%m'),
 137                     # '3' needed for when no leading zero.
 138                     ('2', '%w'), ('10', '%I')]
 139         replacement_pairs.extend([(tz, "%Z") for tz_values in self.timezone
 140                                                 for tz in tz_values])
 141         for offset,directive in ((0,'%c'), (1,'%x'), (2,'%X')):
 142             current_format = date_time[offset]
 143             for old, new in replacement_pairs:
 144                 # Must deal with possible lack of locale info
 145                 # manifesting itself as the empty string (e.g., Swedish's
 146                 # lack of AM/PM info) or a platform returning a tuple of empty
 147                 # strings (e.g., MacOS 9 having timezone as ('','')).
 148                 if old:
 149                     current_format = current_format.replace(old, new)
 150             # If %W is used, then Sunday, 2005-01-03 will fall on week 0 since
 151             # 2005-01-03 occurs before the first Monday of the year.  Otherwise
 152             # %U is used.
 153             time_tuple = time.struct_time((1999,1,3,1,1,1,6,3,0))
 154             if '00' in time.strftime(directive, time_tuple):
 155                 U_W = '%W'
 156             else:
 157                 U_W = '%U'
 158             date_time[offset] = current_format.replace('11', U_W)
 159         self.LC_date_time = date_time[0]
 160         self.LC_date = date_time[1]
 161         self.LC_time = date_time[2]
 162
 163     def __calc_timezone(self):
 164         # Set self.timezone by using time.tzname.
 165         # Do not worry about possibility of time.tzname[0] == timetzname[1]
 166         # and time.daylight; handle that in strptime .
 167         try:
 168             time.tzset()
 169         except AttributeError:
 170             pass
 171         no_saving = frozenset(["utc", "gmt", time.tzname[0].lower()])
 172         if time.daylight:
 173             has_saving = frozenset([time.tzname[1].lower()])
 174         else:
 175             has_saving = frozenset()
 176         self.timezone = (no_saving, has_saving)
 177
 178
 179 class TimeRE(dict):
 180     """Handle conversion from format directives to regexes."""
 181
 182     def __init__(self, locale_time=None):
 183         """Create keys/values.
 184
 185         Order of execution is important for dependency reasons.
 186
 187         """
 188         if locale_time:
 189             self.locale_time = locale_time
 190         else:
 191             self.locale_time = LocaleTime()
 192         base = super(TimeRE, self)
 193         base.__init__({
 194             # The " \d" part of the regex is to make %c from ANSI C work
 195             'd': r"(?P<d>3[0-1]|[1-2]\d|0[1-9]|[1-9]| [1-9])",
 196             'H': r"(?P<H>2[0-3]|[0-1]\d|\d)",
 197             'I': r"(?P<I>1[0-2]|0[1-9]|[1-9])",
 198             'j': r"(?P<j>36[0-6]|3[0-5]\d|[1-2]\d\d|0[1-9]\d|00[1-9]|[1-9]\d|0[1-9]|[1-9])",
 199             'm': r"(?P<m>1[0-2]|0[1-9]|[1-9])",
 200             'M': r"(?P<M>[0-5]\d|\d)",
 201             'S': r"(?P<S>6[0-1]|[0-5]\d|\d)",
 202             'U': r"(?P<U>5[0-3]|[0-4]\d|\d)",
 203             'w': r"(?P<w>[0-6])",
 204             # W is set below by using 'U'
 205             'y': r"(?P<y>\d\d)",
 206             #XXX: Does 'Y' need to worry about having less or more than
 207             #     4 digits?
 208             'Y': r"(?P<Y>\d\d\d\d)",
 209             'A': self.__seqToRE(self.locale_time.f_weekday, 'A'),
 210             'a': self.__seqToRE(self.locale_time.a_weekday, 'a'),
 211             'B': self.__seqToRE(self.locale_time.f_month[1:], 'B'),
 212             'b': self.__seqToRE(self.locale_time.a_month[1:], 'b'),
 213             'p': self.__seqToRE(self.locale_time.am_pm, 'p'),
 214             'Z': self.__seqToRE((tz for tz_names in self.locale_time.timezone
 215                                         for tz in tz_names),
 216                                 'Z'),
 217             '%': '%'})
 218         base.__setitem__('W', base.__getitem__('U').replace('U', 'W'))
 219         base.__setitem__('c', self.pattern(self.locale_time.LC_date_time))
 220         base.__setitem__('x', self.pattern(self.locale_time.LC_date))
 221         base.__setitem__('X', self.pattern(self.locale_time.LC_time))
 222
 223     def __seqToRE(self, to_convert, directive):
 224         """Convert a list to a regex string for matching a directive.
 225
 226         Want possible matching values to be from longest to shortest.  This
 227         prevents the possibility of a match occuring for a value that also
 228         a substring of a larger value that should have matched (e.g., 'abc'
 229         matching when 'abcdef' should have been the match).
 230
 231         """
 232         to_convert = sorted(to_convert, key=len, reverse=True)
 233         for value in to_convert:
 234             if value != '':
 235                 break
 236         else:
 237             return ''
 238         regex = '|'.join(re_escape(stuff) for stuff in to_convert)
 239         regex = '(?P<%s>%s' % (directive, regex)
 240         return '%s)' % regex
 241
 242     def pattern(self, format):
 243         """Return regex pattern for the format string.
 244
 245         Need to make sure that any characters that might be interpreted as
 246         regex syntax are escaped.
 247
 248         """
 249         processed_format = ''
 250         # The sub() call escapes all characters that might be misconstrued
 251         # as regex syntax.  Cannot use re.escape since we have to deal with
 252         # format directives (%m, etc.).
 253         regex_chars = re_compile(r"([\\.^$*+?\(\){}\[\]|])")
 254         format = regex_chars.sub(r"\\\1", format)
 255         whitespace_replacement = re_compile('\s+')
 256         format = whitespace_replacement.sub('\s*', format)
 257         while '%' in format:
 258             directive_index = format.index('%')+1
 259             processed_format = "%s%s%s" % (processed_format,
 260                                            format[:directive_index-1],
 261                                            self[format[directive_index]])
 262             format = format[directive_index+1:]
 263         return "%s%s" % (processed_format, format)
 264
 265     def compile(self, format):
 266         """Return a compiled re object for the format string."""
 267         return re_compile(self.pattern(format), IGNORECASE)
 268
 269 _cache_lock = _thread_allocate_lock()
 270 # DO NOT modify _TimeRE_cache or _regex_cache without acquiring the cache lock
 271 # first!
 272 _TimeRE_cache = TimeRE()
 273 _CACHE_MAX_SIZE = 5 # Max number of regexes stored in _regex_cache
 274 _regex_cache = {}
 275
 276 def strptime(data_string, format="%a %b %d %H:%M:%S %Y"):
 277     """Return a time struct based on the input string and the format string."""
 278     global _TimeRE_cache, _regex_cache
 279     _cache_lock.acquire()
 280     try:
 281         time_re = _TimeRE_cache
 282         locale_time = time_re.locale_time
 283         if _getlang() != locale_time.lang:
 284             _TimeRE_cache = TimeRE()
 285             _regex_cache = {}
 286         if len(_regex_cache) > _CACHE_MAX_SIZE:
 287             _regex_cache.clear()
 288         format_regex = _regex_cache.get(format)
 289         if not format_regex:
 290             try:
 291                 format_regex = time_re.compile(format)
 292             # KeyError raised when a bad format is found; can be specified as
 293             # \\, in which case it was a stray % but with a space after it
 294             except KeyError, err:
 295                 bad_directive = err.args[0]
 296                 if bad_directive == "\\":
 297                     bad_directive = "%"
 298                 del err
 299                 raise ValueError("'%s' is a bad directive in format '%s'" %
 300                                     (bad_directive, format))
 301             # IndexError only occurs when the format string is "%"
 302             except IndexError:
 303                 raise ValueError("stray %% in format '%s'" % format)
 304             _regex_cache[format] = format_regex
 305     finally:
 306         _cache_lock.release()
 307     found = format_regex.match(data_string)
 308     if not found:
 309         raise ValueError("time data did not match format:  data=%s  fmt=%s" %
 310                          (data_string, format))
 311     if len(data_string) != found.end():
 312         raise ValueError("unconverted data remains: %s" %
 313                           data_string[found.end():])
 314     year = 1900
 315     month = day = 1
 316     hour = minute = second = 0
 317     tz = -1
 318     # Default to -1 to signify that values not known; not critical to have,
 319     # though
 320     week_of_year = -1
 321     week_of_year_start = -1
 322     # weekday and julian defaulted to -1 so as to signal need to calculate
 323     # values
 324     weekday = julian = -1
 325     found_dict = found.groupdict()
 326     for group_key in found_dict.iterkeys():
 327         # Directives not explicitly handled below:
 328         #   c, x, X
 329         #      handled by making out of other directives
 330         #   U, W
 331         #      worthless without day of the week
 332         if group_key == 'y':
 333             year = int(found_dict['y'])
 334             # Open Group specification for strptime() states that a %y
 335             #value in the range of [00, 68] is in the century 2000, while
 336             #[69,99] is in the century 1900
 337             if year <= 68:
 338                 year += 2000
 339             else:
 340                 year += 1900
 341         elif group_key == 'Y':
 342             year = int(found_dict['Y'])
 343         elif group_key == 'm':
 344             month = int(found_dict['m'])
 345         elif group_key == 'B':
 346             month = locale_time.f_month.index(found_dict['B'].lower())
 347         elif group_key == 'b':
 348             month = locale_time.a_month.index(found_dict['b'].lower())
 349         elif group_key == 'd':
 350             day = int(found_dict['d'])
 351         elif group_key == 'H':
 352             hour = int(found_dict['H'])
 353         elif group_key == 'I':
 354             hour = int(found_dict['I'])
 355             ampm = found_dict.get('p', '').lower()
 356             # If there was no AM/PM indicator, we'll treat this like AM
 357             if ampm in ('', locale_time.am_pm[0]):
 358                 # We're in AM so the hour is correct unless we're
 359                 # looking at 12 midnight.
 360                 # 12 midnight == 12 AM == hour 0
 361                 if hour == 12:
 362                     hour = 0
 363             elif ampm == locale_time.am_pm[1]:
 364                 # We're in PM so we need to add 12 to the hour unless
 365                 # we're looking at 12 noon.
 366                 # 12 noon == 12 PM == hour 12
 367                 if hour != 12:
 368                     hour += 12
 369         elif group_key == 'M':
 370             minute = int(found_dict['M'])
 371         elif group_key == 'S':
 372             second = int(found_dict['S'])
 373         elif group_key == 'A':
 374             weekday = locale_time.f_weekday.index(found_dict['A'].lower())
 375         elif group_key == 'a':
 376             weekday = locale_time.a_weekday.index(found_dict['a'].lower())
 377         elif group_key == 'w':
 378             weekday = int(found_dict['w'])
 379             if weekday == 0:
 380                 weekday = 6
 381             else:
 382                 weekday -= 1
 383         elif group_key == 'j':
 384             julian = int(found_dict['j'])
 385         elif group_key in ('U', 'W'):
 386             week_of_year = int(found_dict[group_key])
 387             if group_key == 'U':
 388                 # U starts week on Sunday
 389                 week_of_year_start = 6
 390             else:
 391                 # W starts week on Monday
 392                 week_of_year_start = 0
 393         elif group_key == 'Z':
 394             # Since -1 is default value only need to worry about setting tz if
 395             # it can be something other than -1.
 396             found_zone = found_dict['Z'].lower()
 397             for value, tz_values in enumerate(locale_time.timezone):
 398                 if found_zone in tz_values:
 399                     # Deal with bad locale setup where timezone names are the
 400                     # same and yet time.daylight is true; too ambiguous to
 401                     # be able to tell what timezone has daylight savings
 402                     if (time.tzname[0] == time.tzname[1] and
 403                        time.daylight and found_zone not in ("utc", "gmt")):
 404                         break
 405                     else:
 406                         tz = value
 407                         break
 408     # If we know the week of the year and what day of that week, we can figure
 409     # out the Julian day of the year
 410     # Calculations below assume 0 is a Monday
 411     if julian == -1 and week_of_year != -1 and weekday != -1:
 412         # Calculate how many days in week 0
 413         first_weekday = datetime_date(year, 1, 1).weekday()
 414         preceeding_days = 7 - first_weekday
 415         if preceeding_days == 7:
 416             preceeding_days = 0
 417         # Adjust for U directive so that calculations are not dependent on
 418         # directive used to figure out week of year
 419         if weekday == 6 and week_of_year_start == 6:
 420             week_of_year -= 1
 421         # If a year starts and ends on a Monday but a week is specified to
 422         # start on a Sunday we need to up the week to counter-balance the fact
 423         # that with %W that first Monday starts week 1 while with %U that is
 424         # week 0 and thus shifts everything by a week
 425         if weekday == 0 and first_weekday == 0 and week_of_year_start == 6:
 426             week_of_year += 1
 427         # If in week 0, then just figure out how many days from Jan 1 to day of
 428         # week specified, else calculate by multiplying week of year by 7,
 429         # adding in days in week 0, and the number of days from Monday to the
 430         # day of the week
 431         if week_of_year == 0:
 432             julian = 1 + weekday - first_weekday
 433         else:
 434             days_to_week = preceeding_days + (7 * (week_of_year - 1))
 435             julian = 1 + days_to_week + weekday
 436     # Cannot pre-calculate datetime_date() since can change in Julian
 437     #calculation and thus could have different value for the day of the week
 438     #calculation
 439     if julian == -1:
 440         # Need to add 1 to result since first day of the year is 1, not 0.
 441         julian = datetime_date(year, month, day).toordinal() - \
 442                   datetime_date(year, 1, 1).toordinal() + 1
 443     else:  # Assume that if they bothered to include Julian day it will
 444            #be accurate
 445         datetime_result = datetime_date.fromordinal((julian - 1) + datetime_date(year, 1, 1).toordinal())
 446         year = datetime_result.year
 447         month = datetime_result.month
 448         day = datetime_result.day
 449     if weekday == -1:
 450         weekday = datetime_date(year, month, day).weekday()
 451     return time.struct_time((year, month, day,
 452                              hour, minute, second,
 453                              weekday, julian, tz))