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