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cpython/Lib/_strptime.py
Brett Cannon 5d0bf9446b Change time.strptime() to raise ValueError whenever there is an error in the 
format string.  Before exceptions generated by the internal code propagated up
to the user and were not helpful.

Closes bug #1340337.
2005-11-02 23:04:26 +00:00

454 lines
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"""Strptime-related classes and functions.
CLASSES:
LocaleTime -- Discovers and stores locale-specific time information
TimeRE -- Creates regexes for pattern matching a string of text containing
time information
FUNCTIONS:
_getlang -- Figure out what language is being used for the locale
strptime -- Calculates the time struct represented by the passed-in string
"""
import time
import locale
import calendar
from re import compile as re_compile
from re import IGNORECASE
from re import escape as re_escape
from datetime import date as datetime_date
try:
from thread import allocate_lock as _thread_allocate_lock
except:
from dummy_thread import allocate_lock as _thread_allocate_lock
__author__ = "Brett Cannon"
__email__ = "brett@python.org"
__all__ = ['strptime']
def _getlang():
# Figure out what the current language is set to.
return locale.getlocale(locale.LC_TIME)
class LocaleTime(object):
"""Stores and handles locale-specific information related to time.
ATTRIBUTES:
f_weekday -- full weekday names (7-item list)
a_weekday -- abbreviated weekday names (7-item list)
f_month -- full month names (13-item list; dummy value in [0], which
is added by code)
a_month -- abbreviated month names (13-item list, dummy value in
[0], which is added by code)
am_pm -- AM/PM representation (2-item list)
LC_date_time -- format string for date/time representation (string)
LC_date -- format string for date representation (string)
LC_time -- format string for time representation (string)
timezone -- daylight- and non-daylight-savings timezone representation
(2-item list of sets)
lang -- Language used by instance (2-item tuple)
"""
def __init__(self):
"""Set all attributes.
Order of methods called matters for dependency reasons.
The locale language is set at the offset and then checked again before
exiting. This is to make sure that the attributes were not set with a
mix of information from more than one locale. This would most likely
happen when using threads where one thread calls a locale-dependent
function while another thread changes the locale while the function in
the other thread is still running. Proper coding would call for
locks to prevent changing the locale while locale-dependent code is
running. The check here is done in case someone does not think about
doing this.
Only other possible issue is if someone changed the timezone and did
not call tz.tzset . That is an issue for the programmer, though,
since changing the timezone is worthless without that call.
"""
self.lang = _getlang()
self.__calc_weekday()
self.__calc_month()
self.__calc_am_pm()
self.__calc_timezone()
self.__calc_date_time()
if _getlang() != self.lang:
raise ValueError("locale changed during initialization")
def __pad(self, seq, front):
# Add '' to seq to either the front (is True), else the back.
seq = list(seq)
if front:
seq.insert(0, '')
else:
seq.append('')
return seq
def __calc_weekday(self):
# Set self.a_weekday and self.f_weekday using the calendar
# module.
a_weekday = [calendar.day_abbr[i].lower() for i in range(7)]
f_weekday = [calendar.day_name[i].lower() for i in range(7)]
self.a_weekday = a_weekday
self.f_weekday = f_weekday
def __calc_month(self):
# Set self.f_month and self.a_month using the calendar module.
a_month = [calendar.month_abbr[i].lower() for i in range(13)]
f_month = [calendar.month_name[i].lower() for i in range(13)]
self.a_month = a_month
self.f_month = f_month
def __calc_am_pm(self):
# Set self.am_pm by using time.strftime().
# The magic date (1999,3,17,hour,44,55,2,76,0) is not really that
# magical; just happened to have used it everywhere else where a
# static date was needed.
am_pm = []
for hour in (01,22):
time_tuple = time.struct_time((1999,3,17,hour,44,55,2,76,0))
am_pm.append(time.strftime("%p", time_tuple).lower())
self.am_pm = am_pm
def __calc_date_time(self):
# Set self.date_time, self.date, & self.time by using
# time.strftime().
# Use (1999,3,17,22,44,55,2,76,0) for magic date because the amount of
# overloaded numbers is minimized. The order in which searches for
# values within the format string is very important; it eliminates
# possible ambiguity for what something represents.
time_tuple = time.struct_time((1999,3,17,22,44,55,2,76,0))
date_time = [None, None, None]
date_time[0] = time.strftime("%c", time_tuple).lower()
date_time[1] = time.strftime("%x", time_tuple).lower()
date_time[2] = time.strftime("%X", time_tuple).lower()
replacement_pairs = [('%', '%%'), (self.f_weekday[2], '%A'),
(self.f_month[3], '%B'), (self.a_weekday[2], '%a'),
(self.a_month[3], '%b'), (self.am_pm[1], '%p'),
('1999', '%Y'), ('99', '%y'), ('22', '%H'),
('44', '%M'), ('55', '%S'), ('76', '%j'),
('17', '%d'), ('03', '%m'), ('3', '%m'),
# '3' needed for when no leading zero.
('2', '%w'), ('10', '%I')]
replacement_pairs.extend([(tz, "%Z") for tz_values in self.timezone
for tz in tz_values])
for offset,directive in ((0,'%c'), (1,'%x'), (2,'%X')):
current_format = date_time[offset]
for old, new in replacement_pairs:
# Must deal with possible lack of locale info
# manifesting itself as the empty string (e.g., Swedish's
# lack of AM/PM info) or a platform returning a tuple of empty
# strings (e.g., MacOS 9 having timezone as ('','')).
if old:
current_format = current_format.replace(old, new)
# If %W is used, then Sunday, 2005-01-03 will fall on week 0 since
# 2005-01-03 occurs before the first Monday of the year. Otherwise
# %U is used.
time_tuple = time.struct_time((1999,1,3,1,1,1,6,3,0))
if '00' in time.strftime(directive, time_tuple):
U_W = '%W'
else:
U_W = '%U'
date_time[offset] = current_format.replace('11', U_W)
self.LC_date_time = date_time[0]
self.LC_date = date_time[1]
self.LC_time = date_time[2]
def __calc_timezone(self):
# Set self.timezone by using time.tzname.
# Do not worry about possibility of time.tzname[0] == timetzname[1]
# and time.daylight; handle that in strptime .
try:
time.tzset()
except AttributeError:
pass
no_saving = frozenset(["utc", "gmt", time.tzname[0].lower()])
if time.daylight:
has_saving = frozenset([time.tzname[1].lower()])
else:
has_saving = frozenset()
self.timezone = (no_saving, has_saving)
class TimeRE(dict):
"""Handle conversion from format directives to regexes."""
def __init__(self, locale_time=None):
"""Create keys/values.
Order of execution is important for dependency reasons.
"""
if locale_time:
self.locale_time = locale_time
else:
self.locale_time = LocaleTime()
base = super(TimeRE, self)
base.__init__({
# The " \d" part of the regex is to make %c from ANSI C work
'd': r"(?P<d>3[0-1]|[1-2]\d|0[1-9]|[1-9]| [1-9])",
'H': r"(?P<H>2[0-3]|[0-1]\d|\d)",
'I': r"(?P<I>1[0-2]|0[1-9]|[1-9])",
'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])",
'm': r"(?P<m>1[0-2]|0[1-9]|[1-9])",
'M': r"(?P<M>[0-5]\d|\d)",
'S': r"(?P<S>6[0-1]|[0-5]\d|\d)",
'U': r"(?P<U>5[0-3]|[0-4]\d|\d)",
'w': r"(?P<w>[0-6])",
# W is set below by using 'U'
'y': r"(?P<y>\d\d)",
#XXX: Does 'Y' need to worry about having less or more than
# 4 digits?
'Y': r"(?P<Y>\d\d\d\d)",
'A': self.__seqToRE(self.locale_time.f_weekday, 'A'),
'a': self.__seqToRE(self.locale_time.a_weekday, 'a'),
'B': self.__seqToRE(self.locale_time.f_month[1:], 'B'),
'b': self.__seqToRE(self.locale_time.a_month[1:], 'b'),
'p': self.__seqToRE(self.locale_time.am_pm, 'p'),
'Z': self.__seqToRE((tz for tz_names in self.locale_time.timezone
for tz in tz_names),
'Z'),
'%': '%'})
base.__setitem__('W', base.__getitem__('U').replace('U', 'W'))
base.__setitem__('c', self.pattern(self.locale_time.LC_date_time))
base.__setitem__('x', self.pattern(self.locale_time.LC_date))
base.__setitem__('X', self.pattern(self.locale_time.LC_time))
def __seqToRE(self, to_convert, directive):
"""Convert a list to a regex string for matching a directive.
Want possible matching values to be from longest to shortest. This
prevents the possibility of a match occuring for a value that also
a substring of a larger value that should have matched (e.g., 'abc'
matching when 'abcdef' should have been the match).
"""
to_convert = sorted(to_convert, key=len, reverse=True)
for value in to_convert:
if value != '':
break
else:
return ''
regex = '|'.join(re_escape(stuff) for stuff in to_convert)
regex = '(?P<%s>%s' % (directive, regex)
return '%s)' % regex
def pattern(self, format):
"""Return regex pattern for the format string.
Need to make sure that any characters that might be interpreted as
regex syntax are escaped.
"""
processed_format = ''
# The sub() call escapes all characters that might be misconstrued
# as regex syntax. Cannot use re.escape since we have to deal with
# format directives (%m, etc.).
regex_chars = re_compile(r"([\\.^$*+?\(\){}\[\]|])")
format = regex_chars.sub(r"\\\1", format)
whitespace_replacement = re_compile('\s+')
format = whitespace_replacement.sub('\s*', format)
while '%' in format:
directive_index = format.index('%')+1
processed_format = "%s%s%s" % (processed_format,
format[:directive_index-1],
self[format[directive_index]])
format = format[directive_index+1:]
return "%s%s" % (processed_format, format)
def compile(self, format):
"""Return a compiled re object for the format string."""
return re_compile(self.pattern(format), IGNORECASE)
_cache_lock = _thread_allocate_lock()
# DO NOT modify _TimeRE_cache or _regex_cache without acquiring the cache lock
# first!
_TimeRE_cache = TimeRE()
_CACHE_MAX_SIZE = 5 # Max number of regexes stored in _regex_cache
_regex_cache = {}
def strptime(data_string, format="%a %b %d %H:%M:%S %Y"):
"""Return a time struct based on the input string and the format string."""
global _TimeRE_cache, _regex_cache
_cache_lock.acquire()
try:
time_re = _TimeRE_cache
locale_time = time_re.locale_time
if _getlang() != locale_time.lang:
_TimeRE_cache = TimeRE()
_regex_cache = {}
if len(_regex_cache) > _CACHE_MAX_SIZE:
_regex_cache.clear()
format_regex = _regex_cache.get(format)
if not format_regex:
try:
format_regex = time_re.compile(format)
# KeyError raised when a bad format is found; can be specified as
# \\, in which case it was a stray % but with a space after it
except KeyError, err:
bad_directive = err.args[0]
if bad_directive == "\\":
bad_directive = "%"
del err
raise ValueError("'%s' is a bad directive in format '%s'" %
(bad_directive, format))
# IndexError only occurs when the format string is "%"
except IndexError:
raise ValueError("stray %% in format '%s'" % format)
_regex_cache[format] = format_regex
finally:
_cache_lock.release()
found = format_regex.match(data_string)
if not found:
raise ValueError("time data did not match format: data=%s fmt=%s" %
(data_string, format))
if len(data_string) != found.end():
raise ValueError("unconverted data remains: %s" %
data_string[found.end():])
year = 1900
month = day = 1
hour = minute = second = 0
tz = -1
# Default to -1 to signify that values not known; not critical to have,
# though
week_of_year = -1
week_of_year_start = -1
# weekday and julian defaulted to -1 so as to signal need to calculate
# values
weekday = julian = -1
found_dict = found.groupdict()
for group_key in found_dict.iterkeys():
# Directives not explicitly handled below:
# c, x, X
# handled by making out of other directives
# U, W
# worthless without day of the week
if group_key == 'y':
year = int(found_dict['y'])
# Open Group specification for strptime() states that a %y
#value in the range of [00, 68] is in the century 2000, while
#[69,99] is in the century 1900
if year <= 68:
year += 2000
else:
year += 1900
elif group_key == 'Y':
year = int(found_dict['Y'])
elif group_key == 'm':
month = int(found_dict['m'])
elif group_key == 'B':
month = locale_time.f_month.index(found_dict['B'].lower())
elif group_key == 'b':
month = locale_time.a_month.index(found_dict['b'].lower())
elif group_key == 'd':
day = int(found_dict['d'])
elif group_key == 'H':
hour = int(found_dict['H'])
elif group_key == 'I':
hour = int(found_dict['I'])
ampm = found_dict.get('p', '').lower()
# If there was no AM/PM indicator, we'll treat this like AM
if ampm in ('', locale_time.am_pm[0]):
# We're in AM so the hour is correct unless we're
# looking at 12 midnight.
# 12 midnight == 12 AM == hour 0
if hour == 12:
hour = 0
elif ampm == locale_time.am_pm[1]:
# We're in PM so we need to add 12 to the hour unless
# we're looking at 12 noon.
# 12 noon == 12 PM == hour 12
if hour != 12:
hour += 12
elif group_key == 'M':
minute = int(found_dict['M'])
elif group_key == 'S':
second = int(found_dict['S'])
elif group_key == 'A':
weekday = locale_time.f_weekday.index(found_dict['A'].lower())
elif group_key == 'a':
weekday = locale_time.a_weekday.index(found_dict['a'].lower())
elif group_key == 'w':
weekday = int(found_dict['w'])
if weekday == 0:
weekday = 6
else:
weekday -= 1
elif group_key == 'j':
julian = int(found_dict['j'])
elif group_key in ('U', 'W'):
week_of_year = int(found_dict[group_key])
if group_key == 'U':
# U starts week on Sunday
week_of_year_start = 6
else:
# W starts week on Monday
week_of_year_start = 0
elif group_key == 'Z':
# Since -1 is default value only need to worry about setting tz if
# it can be something other than -1.
found_zone = found_dict['Z'].lower()
for value, tz_values in enumerate(locale_time.timezone):
if found_zone in tz_values:
# Deal with bad locale setup where timezone names are the
# same and yet time.daylight is true; too ambiguous to
# be able to tell what timezone has daylight savings
if (time.tzname[0] == time.tzname[1] and
time.daylight and found_zone not in ("utc", "gmt")):
break
else:
tz = value
break
# If we know the week of the year and what day of that week, we can figure
# out the Julian day of the year
# Calculations below assume 0 is a Monday
if julian == -1 and week_of_year != -1 and weekday != -1:
# Calculate how many days in week 0
first_weekday = datetime_date(year, 1, 1).weekday()
preceeding_days = 7 - first_weekday
if preceeding_days == 7:
preceeding_days = 0
# Adjust for U directive so that calculations are not dependent on
# directive used to figure out week of year
if weekday == 6 and week_of_year_start == 6:
week_of_year -= 1
# If a year starts and ends on a Monday but a week is specified to
# start on a Sunday we need to up the week to counter-balance the fact
# that with %W that first Monday starts week 1 while with %U that is
# week 0 and thus shifts everything by a week
if weekday == 0 and first_weekday == 0 and week_of_year_start == 6:
week_of_year += 1
# If in week 0, then just figure out how many days from Jan 1 to day of
# week specified, else calculate by multiplying week of year by 7,
# adding in days in week 0, and the number of days from Monday to the
# day of the week
if week_of_year == 0:
julian = 1 + weekday - first_weekday
else:
days_to_week = preceeding_days + (7 * (week_of_year - 1))
julian = 1 + days_to_week + weekday
# Cannot pre-calculate datetime_date() since can change in Julian
#calculation and thus could have different value for the day of the week
#calculation
if julian == -1:
# Need to add 1 to result since first day of the year is 1, not 0.
julian = datetime_date(year, month, day).toordinal() - \
datetime_date(year, 1, 1).toordinal() + 1
else: # Assume that if they bothered to include Julian day it will
#be accurate
datetime_result = datetime_date.fromordinal((julian - 1) + datetime_date(year, 1, 1).toordinal())
year = datetime_result.year
month = datetime_result.month
day = datetime_result.day
if weekday == -1:
weekday = datetime_date(year, month, day).weekday()
return time.struct_time((year, month, day,
hour, minute, second,
weekday, julian, tz))
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