94 lines
2.9 KiB
Python
94 lines
2.9 KiB
Python
"""Functions to parse datetime objects."""
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# We're using regular expressions rather than time.strptime because:
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# - they provide both validation and parsing,
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# - they're more flexible for datetimes,
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# - the date/datetime/time constructors produce friendlier error messages.
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import datetime
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import re
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from django.utils.timezone import utc
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from django.utils.tzinfo import FixedOffset
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date_re = re.compile(
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r'(?P<year>\d{4})-(?P<month>\d{1,2})-(?P<day>\d{1,2})$'
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)
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datetime_re = re.compile(
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r'(?P<year>\d{4})-(?P<month>\d{1,2})-(?P<day>\d{1,2})'
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r'[T ](?P<hour>\d{1,2}):(?P<minute>\d{1,2})'
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r'(?::(?P<second>\d{1,2})(?:\.(?P<microsecond>\d{1,6})\d{0,6})?)?'
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r'(?P<tzinfo>Z|[+-]\d{1,2}:\d{1,2})?$'
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)
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time_re = re.compile(
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r'(?P<hour>\d{1,2}):(?P<minute>\d{1,2})'
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r'(?::(?P<second>\d{1,2})(?:\.(?P<microsecond>\d{1,6})\d{0,6})?)?'
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)
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def parse_date(value):
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"""Parse a string and return a datetime.date.
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Raise ValueError if the input is well formatted but not a valid date.
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Return None if the input isn't well formatted.
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"""
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match = date_re.match(value)
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if match:
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kw = dict((k, int(v)) for k, v in match.groupdict().iteritems())
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return datetime.date(**kw)
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def parse_time(value):
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"""Parse a string and return a datetime.time.
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This function doesn't support time zone offsets.
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Sub-microsecond precision is accepted, but ignored.
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Raise ValueError if the input is well formatted but not a valid time.
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Return None if the input isn't well formatted, in particular if it
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contains an offset.
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"""
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match = time_re.match(value)
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if match:
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kw = match.groupdict()
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if kw['microsecond']:
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kw['microsecond'] = kw['microsecond'].ljust(6, '0')
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kw = dict((k, int(v)) for k, v in kw.iteritems() if v is not None)
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return datetime.time(**kw)
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def parse_datetime(value):
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"""Parse a string and return a datetime.datetime.
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This function supports time zone offsets. When the input contains one,
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the output uses an instance of FixedOffset as tzinfo.
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Sub-microsecond precision is accepted, but ignored.
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Raise ValueError if the input is well formatted but not a valid datetime.
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Return None if the input isn't well formatted.
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"""
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match = datetime_re.match(value)
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if match:
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kw = match.groupdict()
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if kw['microsecond']:
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kw['microsecond'] = kw['microsecond'].ljust(6, '0')
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tzinfo = kw.pop('tzinfo')
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if tzinfo == 'Z':
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tzinfo = utc
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elif tzinfo is not None:
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offset = 60 * int(tzinfo[1:3]) + int(tzinfo[4:6])
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if tzinfo[0] == '-':
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offset = -offset
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tzinfo = FixedOffset(offset)
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kw = dict((k, int(v)) for k, v in kw.iteritems() if v is not None)
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kw['tzinfo'] = tzinfo
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return datetime.datetime(**kw)
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