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# coding=utf-8
# Copyright 2022-present, the HuggingFace Inc. team.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Contains utilities to handle datetimes in Huggingface Hub."""
from datetime import datetime, timedelta, timezone
# Local machine offset compared to UTC.
# Taken from https://stackoverflow.com/a/3168394.
# `utcoffset()` returns `None` if no offset -> empty timedelta.
UTC_OFFSET = datetime.now(timezone.utc).astimezone().utcoffset() or timedelta()
def parse_datetime(date_string: str) -> datetime:
"""
Parses a date_string returned from the server to a datetime object.
This parser is a weak-parser is the sense that it handles only a single format of
date_string. It is expected that the server format will never change. The
implementation depends only on the standard lib to avoid an external dependency
(python-dateutil). See full discussion about this decision on PR:
https://github.com/huggingface/huggingface_hub/pull/999.
Example:
```py
> parse_datetime('2022-08-19T07:19:38.123Z')
datetime.datetime(2022, 8, 19, 7, 19, 38, 123000, tzinfo=timezone.utc)
```
Args:
date_string (`str`):
A string representing a datetime returned by the Hub server.
String is expected to follow '%Y-%m-%dT%H:%M:%S.%fZ' pattern.
Returns:
A python datetime object.
Raises:
:class:`ValueError`:
If `date_string` cannot be parsed.
"""
try:
# Datetime ending with a Z means "UTC". Here we parse the date as local machine
# timezone and then move it to the appropriate UTC timezone.
# See https://en.wikipedia.org/wiki/ISO_8601#Coordinated_Universal_Time_(UTC)
# Taken from https://stackoverflow.com/a/3168394.
if len(date_string) == 30:
# Means timezoned-timestamp with nanoseconds precision. We need to truncate the last 3 digits.
date_string = date_string[:-4] + "Z"
dt = datetime.strptime(date_string, "%Y-%m-%dT%H:%M:%S.%fZ")
dt += UTC_OFFSET # By default, datetime is not timezoned -> move to UTC time
return dt.astimezone(timezone.utc) # Set explicit timezone
except ValueError as e:
raise ValueError(
f"Cannot parse '{date_string}' as a datetime. Date string is expected to"
" follow '%Y-%m-%dT%H:%M:%S.%fZ' pattern."
) from e
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