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 __all__ = ['strptime']
  26
  27 def _getlang():
  28     # Figure out what the current language is set to.
  29     return locale.getlocale(locale.LC_TIME)
  30
  31 class LocaleTime(object):
  32     """Stores and handles locale-specific information related to time.
  33
  34     ATTRIBUTES:
  35         f_weekday -- full weekday names (7-item list)
  36         a_weekday -- abbreviated weekday names (7-item list)
  37         f_month -- full month names (13-item list; dummy value in [0], which
  38                     is added by code)
  39         a_month -- abbreviated month names (13-item list, dummy value in
  40                     [0], which is added by code)
  41         am_pm -- AM/PM representation (2-item list)
  42         LC_date_time -- format string for date/time representation (string)
  43         LC_date -- format string for date representation (string)
  44         LC_time -- format string for time representation (string)
  45         timezone -- daylight- and non-daylight-savings timezone representation
  46                     (2-item list of sets)
  47         lang -- Language used by instance (2-item tuple)
  48     """
  49
  50     def __init__(self):
  51         """Set all attributes.
  52
  53         Order of methods called matters for dependency reasons.
  54
  55         The locale language is set at the offset and then checked again before
  56         exiting.  This is to make sure that the attributes were not set with a
  57         mix of information from more than one locale.  This would most likely
  58         happen when using threads where one thread calls a locale-dependent
  59         function while another thread changes the locale while the function in
  60         the other thread is still running.  Proper coding would call for
  61         locks to prevent changing the locale while locale-dependent code is
  62         running.  The check here is done in case someone does not think about
  63         doing this.
  64
  65         Only other possible issue is if someone changed the timezone and did
  66         not call tz.tzset .  That is an issue for the programmer, though,
  67         since changing the timezone is worthless without that call.
  68
  69         """
  70         self.lang = _getlang()
  71         self.__calc_weekday()
  72         self.__calc_month()
  73         self.__calc_am_pm()
  74         self.__calc_timezone()
  75         self.__calc_date_time()
  76         if _getlang() != self.lang:
  77             raise ValueError("locale changed during initialization")
  78
  79     def __pad(self, seq, front):
  80         # Add '' to seq to either the front (is True), else the back.
  81         seq = list(seq)
  82         if front:
  83             seq.insert(0, '')
  84         else:
  85             seq.append('')
  86         return seq
  87
  88     def __calc_weekday(self):
  89         # Set self.a_weekday and self.f_weekday using the calendar
  90         # module.
  91         a_weekday = [calendar.day_abbr[i].lower() for i in range(7)]
  92         f_weekday = [calendar.day_name[i].lower() for i in range(7)]
  93         self.a_weekday = a_weekday
  94         self.f_weekday = f_weekday
  95
  96     def __calc_month(self):
  97         # Set self.f_month and self.a_month using the calendar module.
  98         a_month = [calendar.month_abbr[i].lower() for i in range(13)]
  99         f_month = [calendar.month_name[i].lower() for i in range(13)]
 100         self.a_month = a_month
 101         self.f_month = f_month
 102
 103     def __calc_am_pm(self):
 104         # Set self.am_pm by using time.strftime().
 105
 106         # The magic date (1999,3,17,hour,44,55,2,76,0) is not really that
 107         # magical; just happened to have used it everywhere else where a
 108         # static date was needed.
 109         am_pm = []
 110         for hour in (01,22):
 111             time_tuple = time.struct_time((1999,3,17,hour,44,55,2,76,0))
 112             am_pm.append(time.strftime("%p", time_tuple).lower())
 113         self.am_pm = am_pm
 114
 115     def __calc_date_time(self):
 116         # Set self.date_time, self.date, & self.time by using
 117         # time.strftime().
 118
 119         # Use (1999,3,17,22,44,55,2,76,0) for magic date because the amount of
 120         # overloaded numbers is minimized.  The order in which searches for
 121         # values within the format string is very important; it eliminates
 122         # possible ambiguity for what something represents.
 123         time_tuple = time.struct_time((1999,3,17,22,44,55,2,76,0))
 124         date_time = [None, None, None]
 125         date_time[0] = time.strftime("%c", time_tuple).lower()
 126         date_time[1] = time.strftime("%x", time_tuple).lower()
 127         date_time[2] = time.strftime("%X", time_tuple).lower()
 128         replacement_pairs = [('%', '%%'), (self.f_weekday[2], '%A'),
 129                     (self.f_month[3], '%B'), (self.a_weekday[2], '%a'),
 130                     (self.a_month[3], '%b'), (self.am_pm[1], '%p'),
 131                     ('1999', '%Y'), ('99', '%y'), ('22', '%H'),
 132                     ('44', '%M'), ('55', '%S'), ('76', '%j'),
 133                     ('17', '%d'), ('03', '%m'), ('3', '%m'),
 134                     # '3' needed for when no leading zero.
 135                     ('2', '%w'), ('10', '%I')]
 136         replacement_pairs.extend([(tz, "%Z") for tz_values in self.timezone
 137                                                 for tz in tz_values])
 138         for offset,directive in ((0,'%c'), (1,'%x'), (2,'%X')):
 139             current_format = date_time[offset]
 140             for old, new in replacement_pairs:
 141                 # Must deal with possible lack of locale info
 142                 # manifesting itself as the empty string (e.g., Swedish's
 143                 # lack of AM/PM info) or a platform returning a tuple of empty
 144                 # strings (e.g., MacOS 9 having timezone as ('','')).
 145                 if old:
 146                     current_format = current_format.replace(old, new)
 147             # If %W is used, then Sunday, 2005-01-03 will fall on week 0 since
 148             # 2005-01-03 occurs before the first Monday of the year.  Otherwise
 149             # %U is used.
 150             time_tuple = time.struct_time((1999,1,3,1,1,1,6,3,0))
 151             if '00' in time.strftime(directive, time_tuple):
 152                 U_W = '%W'
 153             else:
 154                 U_W = '%U'
 155             date_time[offset] = current_format.replace('11', U_W)
 156         self.LC_date_time = date_time[0]
 157         self.LC_date = date_time[1]
 158         self.LC_time = date_time[2]
 159
 160     def __calc_timezone(self):
 161         # Set self.timezone by using time.tzname.
 162         # Do not worry about possibility of time.tzname[0] == timetzname[1]
 163         # and time.daylight; handle that in strptime .
 164         try:
 165             time.tzset()
 166         except AttributeError:
 167             pass
 168         no_saving = frozenset(["utc", "gmt", time.tzname[0].lower()])
 169         if time.daylight:
 170             has_saving = frozenset([time.tzname[1].lower()])
 171         else:
 172             has_saving = frozenset()
 173         self.timezone = (no_saving, has_saving)
 174
 175
 176 class TimeRE(dict):
 177     """Handle conversion from format directives to regexes."""
 178
 179     def __init__(self, locale_time=None):
 180         """Create keys/values.
 181
 182         Order of execution is important for dependency reasons.
 183
 184         """
 185         if locale_time:
 186             self.locale_time = locale_time
 187         else:
 188             self.locale_time = LocaleTime()
 189         base = super(TimeRE, self)
 190         base.__init__({
 191             # The " \d" part of the regex is to make %c from ANSI C work
 192             'd': r"(?P<d>3[0-1]|[1-2]\d|0[1-9]|[1-9]| [1-9])",
 193             'H': r"(?P<H>2[0-3]|[0-1]\d|\d)",
 194             'I': r"(?P<I>1[0-2]|0[1-9]|[1-9])",
 195             '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])",
 196             'm': r"(?P<m>1[0-2]|0[1-9]|[1-9])",
 197             'M': r"(?P<M>[0-5]\d|\d)",
 198             'S': r"(?P<S>6[0-1]|[0-5]\d|\d)",
 199             'U': r"(?P<U>5[0-3]|[0-4]\d|\d)",
 200             'w': r"(?P<w>[0-6])",
 201             # W is set below by using 'U'
 202             'y': r"(?P<y>\d\d)",
 203             #XXX: Does 'Y' need to worry about having less or more than
 204             #     4 digits?
 205             'Y': r"(?P<Y>\d\d\d\d)",
 206             'A': self.__seqToRE(self.locale_time.f_weekday, 'A'),
 207             'a': self.__seqToRE(self.locale_time.a_weekday, 'a'),
 208             'B': self.__seqToRE(self.locale_time.f_month[1:], 'B'),
 209             'b': self.__seqToRE(self.locale_time.a_month[1:], 'b'),
 210             'p': self.__seqToRE(self.locale_time.am_pm, 'p'),
 211             'Z': self.__seqToRE((tz for tz_names in self.locale_time.timezone
 212                                         for tz in tz_names),
 213                                 'Z'),
 214             '%': '%'})
 215         base.__setitem__('W', base.__getitem__('U').replace('U', 'W'))
 216         base.__setitem__('c', self.pattern(self.locale_time.LC_date_time))
 217         base.__setitem__('x', self.pattern(self.locale_time.LC_date))
 218         base.__setitem__('X', self.pattern(self.locale_time.LC_time))
 219
 220     def __seqToRE(self, to_convert, directive):
 221         """Convert a list to a regex string for matching a directive.
 222
 223         Want possible matching values to be from longest to shortest.  This
 224         prevents the possibility of a match occuring for a value that also
 225         a substring of a larger value that should have matched (e.g., 'abc'
 226         matching when 'abcdef' should have been the match).
 227
 228         """
 229         to_convert = sorted(to_convert, key=len, reverse=True)
 230         for value in to_convert:
 231             if value != '':
 232                 break
 233         else:
 234             return ''
 235         regex = '|'.join(re_escape(stuff) for stuff in to_convert)
 236         regex = '(?P<%s>%s' % (directive, regex)
 237         return '%s)' % regex
 238
 239     def pattern(self, format):
 240         """Return regex pattern for the format string.
 241
 242         Need to make sure that any characters that might be interpreted as
 243         regex syntax are escaped.
 244
 245         """
 246         processed_format = ''
 247         # The sub() call escapes all characters that might be misconstrued
 248         # as regex syntax.  Cannot use re.escape since we have to deal with
 249         # format directives (%m, etc.).
 250         regex_chars = re_compile(r"([\\.^$*+?\(\){}\[\]|])")
 251         format = regex_chars.sub(r"\\\1", format)
 252         whitespace_replacement = re_compile('\s+')
 253         format = whitespace_replacement.sub('\s+', format)
 254         while '%' in format:
 255             directive_index = format.index('%')+1
 256             processed_format = "%s%s%s" % (processed_format,
 257                                            format[:directive_index-1],
 258                                            self[format[directive_index]])
 259             format = format[directive_index+1:]
 260         return "%s%s" % (processed_format, format)
 261
 262     def compile(self, format):
 263         """Return a compiled re object for the format string."""
 264         return re_compile(self.pattern(format), IGNORECASE)
 265
 266 _cache_lock = _thread_allocate_lock()
 267 # DO NOT modify _TimeRE_cache or _regex_cache without acquiring the cache lock
 268 # first!
 269 _TimeRE_cache = TimeRE()
 270 _CACHE_MAX_SIZE = 5 # Max number of regexes stored in _regex_cache
 271 _regex_cache = {}
 272
 273 def _calc_julian_from_U_or_W(year, week_of_year, day_of_week, week_starts_Mon):
 274     """Calculate the Julian day based on the year, week of the year, and day of
 275     the week, with week_start_day representing whether the week of the year
 276     assumes the week starts on Sunday or Monday (6 or 0)."""
 277     first_weekday = datetime_date(year, 1, 1).weekday()
 278     # If we are dealing with the %U directive (week starts on Sunday), it's
 279     # easier to just shift the view to Sunday being the first day of the
 280     # week.
 281     if not week_starts_Mon:
 282         first_weekday = (first_weekday + 1) % 7
 283         day_of_week = (day_of_week + 1) % 7
 284     # Need to watch out for a week 0 (when the first day of the year is not
 285     # the same as that specified by %U or %W).
 286     week_0_length = (7 - first_weekday) % 7
 287     if week_of_year == 0:
 288         return 1 + day_of_week - first_weekday
 289     else:
 290         days_to_week = week_0_length + (7 * (week_of_year - 1))
 291         return 1 + days_to_week + day_of_week
 292
 293
 294 def strptime(data_string, format="%a %b %d %H:%M:%S %Y"):
 295     """Return a time struct based on the input string and the format string."""
 296     global _TimeRE_cache, _regex_cache
 297     with _cache_lock:
 298         if _getlang() != _TimeRE_cache.locale_time.lang:
 299             _TimeRE_cache = TimeRE()
 300             _regex_cache.clear()
 301         if len(_regex_cache) > _CACHE_MAX_SIZE:
 302             _regex_cache.clear()
 303         locale_time = _TimeRE_cache.locale_time
 304         format_regex = _regex_cache.get(format)
 305         if not format_regex:
 306             try:
 307                 format_regex = _TimeRE_cache.compile(format)
 308             # KeyError raised when a bad format is found; can be specified as
 309             # \\, in which case it was a stray % but with a space after it
 310             except KeyError, err:
 311                 bad_directive = err.args[0]
 312                 if bad_directive == "\\":
 313                     bad_directive = "%"
 314                 del err
 315                 raise ValueError("'%s' is a bad directive in format '%s'" %
 316                                     (bad_directive, format))
 317             # IndexError only occurs when the format string is "%"
 318             except IndexError:
 319                 raise ValueError("stray %% in format '%s'" % format)
 320             _regex_cache[format] = format_regex
 321     found = format_regex.match(data_string)
 322     if not found:
 323         raise ValueError("time data %r does not match format %r" %
 324                          (data_string, format))
 325     if len(data_string) != found.end():
 326         raise ValueError("unconverted data remains: %s" %
 327                           data_string[found.end():])
 328     year = 1900
 329     month = day = 1
 330     hour = minute = second = 0
 331     tz = -1
 332     # Default to -1 to signify that values not known; not critical to have,
 333     # though
 334     week_of_year = -1
 335     week_of_year_start = -1
 336     # weekday and julian defaulted to -1 so as to signal need to calculate
 337     # values
 338     weekday = julian = -1
 339     found_dict = found.groupdict()
 340     for group_key in found_dict.iterkeys():
 341         # Directives not explicitly handled below:
 342         #   c, x, X
 343         #      handled by making out of other directives
 344         #   U, W
 345         #      worthless without day of the week
 346         if group_key == 'y':
 347             year = int(found_dict['y'])
 348             # Open Group specification for strptime() states that a %y
 349             #value in the range of [00, 68] is in the century 2000, while
 350             #[69,99] is in the century 1900
 351             if year <= 68:
 352                 year += 2000
 353             else:
 354                 year += 1900
 355         elif group_key == 'Y':
 356             year = int(found_dict['Y'])
 357         elif group_key == 'm':
 358             month = int(found_dict['m'])
 359         elif group_key == 'B':
 360             month = locale_time.f_month.index(found_dict['B'].lower())
 361         elif group_key == 'b':
 362             month = locale_time.a_month.index(found_dict['b'].lower())
 363         elif group_key == 'd':
 364             day = int(found_dict['d'])
 365         elif group_key == 'H':
 366             hour = int(found_dict['H'])
 367         elif group_key == 'I':
 368             hour = int(found_dict['I'])
 369             ampm = found_dict.get('p', '').lower()
 370             # If there was no AM/PM indicator, we'll treat this like AM
 371             if ampm in ('', locale_time.am_pm[0]):
 372                 # We're in AM so the hour is correct unless we're
 373                 # looking at 12 midnight.
 374                 # 12 midnight == 12 AM == hour 0
 375                 if hour == 12:
 376                     hour = 0
 377             elif ampm == locale_time.am_pm[1]:
 378                 # We're in PM so we need to add 12 to the hour unless
 379                 # we're looking at 12 noon.
 380                 # 12 noon == 12 PM == hour 12
 381                 if hour != 12:
 382                     hour += 12
 383         elif group_key == 'M':
 384             minute = int(found_dict['M'])
 385         elif group_key == 'S':
 386             second = int(found_dict['S'])
 387         elif group_key == 'A':
 388             weekday = locale_time.f_weekday.index(found_dict['A'].lower())
 389         elif group_key == 'a':
 390             weekday = locale_time.a_weekday.index(found_dict['a'].lower())
 391         elif group_key == 'w':
 392             weekday = int(found_dict['w'])
 393             if weekday == 0:
 394                 weekday = 6
 395             else:
 396                 weekday -= 1
 397         elif group_key == 'j':
 398             julian = int(found_dict['j'])
 399         elif group_key in ('U', 'W'):
 400             week_of_year = int(found_dict[group_key])
 401             if group_key == 'U':
 402                 # U starts week on Sunday.
 403                 week_of_year_start = 6
 404             else:
 405                 # W starts week on Monday.
 406                 week_of_year_start = 0
 407         elif group_key == 'Z':
 408             # Since -1 is default value only need to worry about setting tz if
 409             # it can be something other than -1.
 410             found_zone = found_dict['Z'].lower()
 411             for value, tz_values in enumerate(locale_time.timezone):
 412                 if found_zone in tz_values:
 413                     # Deal with bad locale setup where timezone names are the
 414                     # same and yet time.daylight is true; too ambiguous to
 415                     # be able to tell what timezone has daylight savings
 416                     if (time.tzname[0] == time.tzname[1] and
 417                        time.daylight and found_zone not in ("utc", "gmt")):
 418                         break
 419                     else:
 420                         tz = value
 421                         break
 422     # If we know the week of the year and what day of that week, we can figure
 423     # out the Julian day of the year.
 424     if julian == -1 and week_of_year != -1 and weekday != -1:
 425         week_starts_Mon = True if week_of_year_start == 0 else False
 426         julian = _calc_julian_from_U_or_W(year, week_of_year, weekday,
 427                                             week_starts_Mon)
 428     # Cannot pre-calculate datetime_date() since can change in Julian
 429     # calculation and thus could have different value for the day of the week
 430     # calculation.
 431     if julian == -1:
 432         # Need to add 1 to result since first day of the year is 1, not 0.
 433         julian = datetime_date(year, month, day).toordinal() - \
 434                   datetime_date(year, 1, 1).toordinal() + 1
 435     else:  # Assume that if they bothered to include Julian day it will
 436            # be accurate.
 437         datetime_result = datetime_date.fromordinal((julian - 1) + datetime_date(year, 1, 1).toordinal())
 438         year = datetime_result.year
 439         month = datetime_result.month
 440         day = datetime_result.day
 441     if weekday == -1:
 442         weekday = datetime_date(year, month, day).weekday()
 443     return time.struct_time((year, month, day,
 444                              hour, minute, second,
 445                              weekday, julian, tz))