"""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.timezone import get_fixed_timezone, utc
date_re = re.compile(
r'(?P<year>\d{4})-(?P<month>\d{1,2})-(?P<day>\d{1,2})$'
)
time_re = re.compile(
r'(?P<hour>\d{1,2}):(?P<minute>\d{1,2})'
r'(?::(?P<second>\d{1,2})(?:\.(?P<microsecond>\d{1,6})\d{0,6})?)?'
)
datetime_re = re.compile(
r'(?P<year>\d{4})-(?P<month>\d{1,2})-(?P<day>\d{1,2})'
r'[T ](?P<hour>\d{1,2}):(?P<minute>\d{1,2})'
r'(?::(?P<second>\d{1,2})(?:\.(?P<microsecond>\d{1,6})\d{0,6})?)?'
r'(?P<tzinfo>Z|[+-]\d{2}(?::?\d{2})?)?$'
)
standard_duration_re = re.compile(
r'^'
r'(?:(?P<days>-?\d+) (days?, )?)?'
r'((?:(?P<hours>-?\d+):)(?=\d+:\d+))?'
r'(?:(?P<minutes>-?\d+):)?'
r'(?P<seconds>-?\d+)'
r'(?:\.(?P<microseconds>\d{1,6})\d{0,6})?'
r'$'
)
# Support the sections of ISO 8601 date representation that are accepted by
# timedelta
iso8601_duration_re = re.compile(
r'^(?P<sign>[-+]?)'
r'P'
r'(?:(?P<days>\d+(.\d+)?)D)?'
r'(?:T'
r'(?:(?P<hours>\d+(.\d+)?)H)?'
r'(?:(?P<minutes>\d+(.\d+)?)M)?'
r'(?:(?P<seconds>\d+(.\d+)?)S)?'
r')?'
r'$'
)
# Support PostgreSQL's day-time interval format, e.g. "3 days 04:05:06". The
# year-month and mixed intervals cannot be converted to a timedelta and thus
# aren't accepted.
postgres_interval_re = re.compile(
r'^'
r'(?:(?P<days>-?\d+) (days? ?))?'
r'(?:(?P<sign>[-+])?'
r'(?P<hours>\d+):'
r'(?P<minutes>\d\d):'
r'(?P<seconds>\d\d)'
r'(?:\.(?P<microseconds>\d{1,6}))?'
r')?$'
)
[docs]def parse_date(value):
"""Parse a string and return a datetime.date.
Raise ValueError if the input is well formatted but not a valid date.
Return None if the input isn't well formatted.
"""
match = date_re.match(value)
if match:
kw = {k: int(v) for k, v in match.groupdict().items()}
return datetime.date(**kw)
[docs]def parse_time(value):
"""Parse a string and return a datetime.time.
This function doesn't support time zone offsets.
Raise ValueError if the input is well formatted but not a valid time.
Return 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()
kw['microsecond'] = kw['microsecond'] and kw['microsecond'].ljust(6, '0')
kw = {k: int(v) for k, v in kw.items() if v is not None}
return datetime.time(**kw)
[docs]def parse_datetime(value):
"""Parse 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.
Raise ValueError if the input is well formatted but not a valid datetime.
Return None if the input isn't well formatted.
"""
match = datetime_re.match(value)
if match:
kw = match.groupdict()
kw['microsecond'] = kw['microsecond'] and 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 kw.items() if v is not None}
kw['tzinfo'] = tzinfo
return datetime.datetime(**kw)
[docs]def parse_duration(value):
"""Parse a duration string and return a datetime.timedelta.
The preferred format for durations in Django is '%d %H:%M:%S.%f'.
Also supports ISO 8601 representation and PostgreSQL's day-time interval
format.
"""
match = (
standard_duration_re.match(value) or
iso8601_duration_re.match(value) or
postgres_interval_re.match(value)
)
if match:
kw = match.groupdict()
days = datetime.timedelta(float(kw.pop('days', 0) or 0))
sign = -1 if kw.pop('sign', '+') == '-' else 1
if kw.get('microseconds'):
kw['microseconds'] = kw['microseconds'].ljust(6, '0')
if kw.get('seconds') and kw.get('microseconds') and kw['seconds'].startswith('-'):
kw['microseconds'] = '-' + kw['microseconds']
kw = {k: float(v) for k, v in kw.items() if v is not None}
return days + sign * datetime.timedelta(**kw)
Oct 31, 2018