48 lines
1.6 KiB
Python
48 lines
1.6 KiB
Python
from datetime import datetime
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from typing import Callable, Literal, cast
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from my.core import datetime_aware
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'''
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Depending on the specific data provider and your level of paranoia you might expect different behaviour.. E.g.:
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- if your objects already have tz info, you might not need to call localize() at all
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- it's safer when either all of your objects are tz aware or all are tz unware, not a mixture
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- you might trust your original timezone, or it might just be UTC, and you want to use something more reasonable
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'''
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TzPolicy = Literal[
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'keep' , # if datetime is tz aware, just preserve it
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'convert', # if datetime is tz aware, convert to provider's tz
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'throw' , # if datetime is tz aware, throw exception
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# todo 'warn'? not sure if very useful
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]
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# backwards compatibility
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Policy = TzPolicy
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def default_policy() -> TzPolicy:
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try:
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from my.config import time as user_config
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return cast(TzPolicy, user_config.tz.policy)
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except Exception as e:
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# todo meh.. need to think how to do this more carefully
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# rationale: do not mess with user's data unless they want
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return 'keep'
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def localize_with_policy(
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lfun: Callable[[datetime], datetime_aware],
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dt: datetime,
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policy: TzPolicy=default_policy()
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) -> datetime_aware:
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tz = dt.tzinfo
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if tz is None:
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return lfun(dt)
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if policy == 'keep':
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return dt
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elif policy == 'convert':
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ldt = lfun(dt.replace(tzinfo=None))
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return dt.astimezone(ldt.tzinfo)
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else: # policy == 'error':
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raise RuntimeError(f"{dt} already has timezone information (use 'policy' argument to adjust this behaviour)")
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