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@dnozay
Created December 19, 2017 20:07
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Datetime utilities extracted from Django code as a single module.

Datetime utilities extracted from Django code as a single module. Mostly copy-paste, so using the same LICENSE.

https://stackoverflow.com/questions/20194496/iso-to-datetime-object-z-is-a-bad-directive

Example:

>>> from datetime_z import parse_datetime
>>> parse_datetime('2013-07-23T15:10:59.342107+01:00')
datetime.datetime(2013, 7, 23, 15, 10, 59, 342107, tzinfo=+0100)
>>> parse_datetime('2013-07-23T15:10:59.34210Z')
datetime.datetime(2013, 7, 23, 15, 10, 59, 342100, tzinfo=UTC)
"""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
# UTC and local time zones
ZERO = datetime.timedelta(0)
class FixedOffset(datetime.tzinfo):
"""
Fixed offset in minutes east from UTC. Taken from Python's docs.
Kept as close as possible to the reference version. __init__ was changed
to make its arguments optional, according to Python's requirement that
tzinfo subclasses can be instantiated without arguments.
"""
def __init__(self, offset=None, name=None):
if offset is not None:
self.__offset = datetime.timedelta(minutes=offset)
if name is not None:
self.__name = name
def utcoffset(self, dt):
return self.__offset
def tzname(self, dt):
return self.__name
def dst(self, dt):
return ZERO
def __repr__(self):
return self.__name
class UTC(datetime.tzinfo):
zone = "UTC"
def utcoffset(self, dt):
return ZERO
def tzname(self, dt):
return "UTC"
def dst(self, dt):
return ZERO
def __repr__(self):
return "UTC"
# UTC time zone as a tzinfo instance.
utc = UTC()
def get_fixed_timezone(offset):
"""Return a tzinfo instance with a fixed offset from UTC."""
if isinstance(offset, datetime.timedelta):
offset = offset.total_seconds() // 60
sign = '-' if offset < 0 else '+'
hhmm = '%02d%02d' % divmod(abs(offset), 60)
name = sign + hhmm
return FixedOffset(offset, name)
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')?$'
)
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)
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()
if kw['microsecond']:
kw['microsecond'] = kw['microsecond'].ljust(6, '0')
kw = {k: int(v) for k, v in kw.items() if v is not None}
return datetime.time(**kw)
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.
>>> from datetime_z import parse_datetime
>>> parse_datetime('2013-07-23T15:10:59.342107+01:00')
datetime.datetime(2013, 7, 23, 15, 10, 59, 342107, tzinfo=+0100)
>>> parse_datetime('2013-07-23T15:10:59.34210Z')
datetime.datetime(2013, 7, 23, 15, 10, 59, 342100, tzinfo=UTC)
"""
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 kw.items() if v is not None}
kw['tzinfo'] = tzinfo
return datetime.datetime(**kw)
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)
if __name__ == "__main__":
import doctest
doctest.testmod()
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Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:
1. Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. Neither the name of Django nor the names of its contributors may be used
to endorse or promote products derived from this software without
specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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