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/Lib/_strptime.py

http://unladen-swallow.googlecode.com/
Python | 454 lines | 363 code | 12 blank | 79 comment | 22 complexity | 61fc98ce5e5c720e60cc3fa5acdd1a72 MD5 | raw file
  1"""Strptime-related classes and functions.
  2
  3CLASSES:
  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
  8FUNCTIONS:
  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"""
 13import time
 14import locale
 15import calendar
 16from re import compile as re_compile
 17from re import IGNORECASE
 18from re import escape as re_escape
 19from datetime import date as datetime_date
 20try:
 21    from thread import allocate_lock as _thread_allocate_lock
 22except:
 23    from dummy_thread import allocate_lock as _thread_allocate_lock
 24
 25__all__ = []
 26
 27def _getlang():
 28    # Figure out what the current language is set to.
 29    return locale.getlocale(locale.LC_TIME)
 30
 31class 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
176class 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            'f': r"(?P<f>[0-9]{1,6})",
194            'H': r"(?P<H>2[0-3]|[0-1]\d|\d)",
195            'I': r"(?P<I>1[0-2]|0[1-9]|[1-9])",
196            '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])",
197            'm': r"(?P<m>1[0-2]|0[1-9]|[1-9])",
198            'M': r"(?P<M>[0-5]\d|\d)",
199            'S': r"(?P<S>6[0-1]|[0-5]\d|\d)",
200            'U': r"(?P<U>5[0-3]|[0-4]\d|\d)",
201            'w': r"(?P<w>[0-6])",
202            # W is set below by using 'U'
203            'y': r"(?P<y>\d\d)",
204            #XXX: Does 'Y' need to worry about having less or more than
205            #     4 digits?
206            'Y': r"(?P<Y>\d\d\d\d)",
207            'A': self.__seqToRE(self.locale_time.f_weekday, 'A'),
208            'a': self.__seqToRE(self.locale_time.a_weekday, 'a'),
209            'B': self.__seqToRE(self.locale_time.f_month[1:], 'B'),
210            'b': self.__seqToRE(self.locale_time.a_month[1:], 'b'),
211            'p': self.__seqToRE(self.locale_time.am_pm, 'p'),
212            'Z': self.__seqToRE((tz for tz_names in self.locale_time.timezone
213                                        for tz in tz_names),
214                                'Z'),
215            '%': '%'})
216        base.__setitem__('W', base.__getitem__('U').replace('U', 'W'))
217        base.__setitem__('c', self.pattern(self.locale_time.LC_date_time))
218        base.__setitem__('x', self.pattern(self.locale_time.LC_date))
219        base.__setitem__('X', self.pattern(self.locale_time.LC_time))
220
221    def __seqToRE(self, to_convert, directive):
222        """Convert a list to a regex string for matching a directive.
223
224        Want possible matching values to be from longest to shortest.  This
225        prevents the possibility of a match occuring for a value that also
226        a substring of a larger value that should have matched (e.g., 'abc'
227        matching when 'abcdef' should have been the match).
228
229        """
230        to_convert = sorted(to_convert, key=len, reverse=True)
231        for value in to_convert:
232            if value != '':
233                break
234        else:
235            return ''
236        regex = '|'.join(re_escape(stuff) for stuff in to_convert)
237        regex = '(?P<%s>%s' % (directive, regex)
238        return '%s)' % regex
239
240    def pattern(self, format):
241        """Return regex pattern for the format string.
242
243        Need to make sure that any characters that might be interpreted as
244        regex syntax are escaped.
245
246        """
247        processed_format = ''
248        # The sub() call escapes all characters that might be misconstrued
249        # as regex syntax.  Cannot use re.escape since we have to deal with
250        # format directives (%m, etc.).
251        regex_chars = re_compile(r"([\\.^$*+?\(\){}\[\]|])")
252        format = regex_chars.sub(r"\\\1", format)
253        whitespace_replacement = re_compile('\s+')
254        format = whitespace_replacement.sub('\s+', format)
255        while '%' in format:
256            directive_index = format.index('%')+1
257            processed_format = "%s%s%s" % (processed_format,
258                                           format[:directive_index-1],
259                                           self[format[directive_index]])
260            format = format[directive_index+1:]
261        return "%s%s" % (processed_format, format)
262
263    def compile(self, format):
264        """Return a compiled re object for the format string."""
265        return re_compile(self.pattern(format), IGNORECASE)
266
267_cache_lock = _thread_allocate_lock()
268# DO NOT modify _TimeRE_cache or _regex_cache without acquiring the cache lock
269# first!
270_TimeRE_cache = TimeRE()
271_CACHE_MAX_SIZE = 5 # Max number of regexes stored in _regex_cache
272_regex_cache = {}
273
274def _calc_julian_from_U_or_W(year, week_of_year, day_of_week, week_starts_Mon):
275    """Calculate the Julian day based on the year, week of the year, and day of
276    the week, with week_start_day representing whether the week of the year
277    assumes the week starts on Sunday or Monday (6 or 0)."""
278    first_weekday = datetime_date(year, 1, 1).weekday()
279    # If we are dealing with the %U directive (week starts on Sunday), it's
280    # easier to just shift the view to Sunday being the first day of the
281    # week.
282    if not week_starts_Mon:
283        first_weekday = (first_weekday + 1) % 7
284        day_of_week = (day_of_week + 1) % 7
285    # Need to watch out for a week 0 (when the first day of the year is not
286    # the same as that specified by %U or %W).
287    week_0_length = (7 - first_weekday) % 7
288    if week_of_year == 0:
289        return 1 + day_of_week - first_weekday
290    else:
291        days_to_week = week_0_length + (7 * (week_of_year - 1))
292        return 1 + days_to_week + day_of_week
293
294
295def _strptime(data_string, format="%a %b %d %H:%M:%S %Y"):
296    """Return a time struct based on the input string and the format string."""
297    global _TimeRE_cache, _regex_cache
298    with _cache_lock:
299        if _getlang() != _TimeRE_cache.locale_time.lang:
300            _TimeRE_cache = TimeRE()
301            _regex_cache.clear()
302        if len(_regex_cache) > _CACHE_MAX_SIZE:
303            _regex_cache.clear()
304        locale_time = _TimeRE_cache.locale_time
305        format_regex = _regex_cache.get(format)
306        if not format_regex:
307            try:
308                format_regex = _TimeRE_cache.compile(format)
309            # KeyError raised when a bad format is found; can be specified as
310            # \\, in which case it was a stray % but with a space after it
311            except KeyError, err:
312                bad_directive = err.args[0]
313                if bad_directive == "\\":
314                    bad_directive = "%"
315                del err
316                raise ValueError("'%s' is a bad directive in format '%s'" %
317                                    (bad_directive, format))
318            # IndexError only occurs when the format string is "%"
319            except IndexError:
320                raise ValueError("stray %% in format '%s'" % format)
321            _regex_cache[format] = format_regex
322    found = format_regex.match(data_string)
323    if not found:
324        raise ValueError("time data %r does not match format %r" %
325                         (data_string, format))
326    if len(data_string) != found.end():
327        raise ValueError("unconverted data remains: %s" %
328                          data_string[found.end():])
329    year = 1900
330    month = day = 1
331    hour = minute = second = fraction = 0
332    tz = -1
333    # Default to -1 to signify that values not known; not critical to have,
334    # though
335    week_of_year = -1
336    week_of_year_start = -1
337    # weekday and julian defaulted to -1 so as to signal need to calculate
338    # values
339    weekday = julian = -1
340    found_dict = found.groupdict()
341    for group_key in found_dict.iterkeys():
342        # Directives not explicitly handled below:
343        #   c, x, X
344        #      handled by making out of other directives
345        #   U, W
346        #      worthless without day of the week
347        if group_key == 'y':
348            year = int(found_dict['y'])
349            # Open Group specification for strptime() states that a %y
350            #value in the range of [00, 68] is in the century 2000, while
351            #[69,99] is in the century 1900
352            if year <= 68:
353                year += 2000
354            else:
355                year += 1900
356        elif group_key == 'Y':
357            year = int(found_dict['Y'])
358        elif group_key == 'm':
359            month = int(found_dict['m'])
360        elif group_key == 'B':
361            month = locale_time.f_month.index(found_dict['B'].lower())
362        elif group_key == 'b':
363            month = locale_time.a_month.index(found_dict['b'].lower())
364        elif group_key == 'd':
365            day = int(found_dict['d'])
366        elif group_key == 'H':
367            hour = int(found_dict['H'])
368        elif group_key == 'I':
369            hour = int(found_dict['I'])
370            ampm = found_dict.get('p', '').lower()
371            # If there was no AM/PM indicator, we'll treat this like AM
372            if ampm in ('', locale_time.am_pm[0]):
373                # We're in AM so the hour is correct unless we're
374                # looking at 12 midnight.
375                # 12 midnight == 12 AM == hour 0
376                if hour == 12:
377                    hour = 0
378            elif ampm == locale_time.am_pm[1]:
379                # We're in PM so we need to add 12 to the hour unless
380                # we're looking at 12 noon.
381                # 12 noon == 12 PM == hour 12
382                if hour != 12:
383                    hour += 12
384        elif group_key == 'M':
385            minute = int(found_dict['M'])
386        elif group_key == 'S':
387            second = int(found_dict['S'])
388        elif group_key == 'f':
389            s = found_dict['f']
390            # Pad to always return microseconds.
391            s += "0" * (6 - len(s))
392            fraction = int(s)
393        elif group_key == 'A':
394            weekday = locale_time.f_weekday.index(found_dict['A'].lower())
395        elif group_key == 'a':
396            weekday = locale_time.a_weekday.index(found_dict['a'].lower())
397        elif group_key == 'w':
398            weekday = int(found_dict['w'])
399            if weekday == 0:
400                weekday = 6
401            else:
402                weekday -= 1
403        elif group_key == 'j':
404            julian = int(found_dict['j'])
405        elif group_key in ('U', 'W'):
406            week_of_year = int(found_dict[group_key])
407            if group_key == 'U':
408                # U starts week on Sunday.
409                week_of_year_start = 6
410            else:
411                # W starts week on Monday.
412                week_of_year_start = 0
413        elif group_key == 'Z':
414            # Since -1 is default value only need to worry about setting tz if
415            # it can be something other than -1.
416            found_zone = found_dict['Z'].lower()
417            for value, tz_values in enumerate(locale_time.timezone):
418                if found_zone in tz_values:
419                    # Deal with bad locale setup where timezone names are the
420                    # same and yet time.daylight is true; too ambiguous to
421                    # be able to tell what timezone has daylight savings
422                    if (time.tzname[0] == time.tzname[1] and
423                       time.daylight and found_zone not in ("utc", "gmt")):
424                        break
425                    else:
426                        tz = value
427                        break
428    # If we know the week of the year and what day of that week, we can figure
429    # out the Julian day of the year.
430    if julian == -1 and week_of_year != -1 and weekday != -1:
431        week_starts_Mon = True if week_of_year_start == 0 else False
432        julian = _calc_julian_from_U_or_W(year, week_of_year, weekday,
433                                            week_starts_Mon)
434    # Cannot pre-calculate datetime_date() since can change in Julian
435    # calculation and thus could have different value for the day of the week
436    # calculation.
437    if julian == -1:
438        # Need to add 1 to result since first day of the year is 1, not 0.
439        julian = datetime_date(year, month, day).toordinal() - \
440                  datetime_date(year, 1, 1).toordinal() + 1
441    else:  # Assume that if they bothered to include Julian day it will
442           # be accurate.
443        datetime_result = datetime_date.fromordinal((julian - 1) + datetime_date(year, 1, 1).toordinal())
444        year = datetime_result.year
445        month = datetime_result.month
446        day = datetime_result.day
447    if weekday == -1:
448        weekday = datetime_date(year, month, day).weekday()
449    return (time.struct_time((year, month, day,
450                              hour, minute, second,
451                              weekday, julian, tz)), fraction)
452
453def _strptime_time(data_string, format="%a %b %d %H:%M:%S %Y"):
454    return _strptime(data_string, format)[0]