Open
Description
datetime.datetime objects created with timezone information cannot be compared to datetime objects without timezone information. This error comes up
TypeError: can't compare offset-naive and offset-aware datetimes
I believe it is possible for the type system to handle distinguishing between these two objects.
I have a proof of concept at my Company that looks something like this. The idea is to distinguish between these two object types and forbid their corresponding comparisons.
class DatetimeWithTimezone(datetime_lib.datetime):
"""Datetime with timezone."""
@overload
def replace(
self,
year: SupportsIndex = ...,
month: SupportsIndex = ...,
day: SupportsIndex = ...,
hour: SupportsIndex = ...,
minute: SupportsIndex = ...,
second: SupportsIndex = ...,
microsecond: SupportsIndex = ...,
tzinfo: _TzInfo = ...,
*,
fold: int = ...,
) -> Self: ...
@overload
def replace(
self,
year: SupportsIndex = ...,
month: SupportsIndex = ...,
day: SupportsIndex = ...,
hour: SupportsIndex = ...,
minute: SupportsIndex = ...,
second: SupportsIndex = ...,
microsecond: SupportsIndex = ...,
tzinfo: None = ...,
*,
fold: int = ...,
) -> DatetimeWithoutTimezone: ...
@overload
def astimezone(self, tz: _TzInfo) -> Self: ...
@overload
def astimezone(self, tz: None) -> DatetimeWithoutTimezone: ...
def utcoffset(self) -> timedelta: ...
def tzname(self) -> str: ...
def dst(self) -> timedelta: ...
def __le__(self, value: DatetimeWithTimezone, /) -> bool: ... # type: ignore[override]
def __lt__(self, value: DatetimeWithTimezone, /) -> bool: ... # type: ignore[override]
def __ge__(self, value: DatetimeWithTimezone, /) -> bool: ... # type: ignore[override]
def __gt__(self, value: DatetimeWithTimezone, /) -> bool: ... # type: ignore[override]
@overload # type: ignore[override]
def __sub__(self, value: Self, /) -> timedelta: ...
@overload
def __sub__(self, value: timedelta, /) -> Self: ...
class DatetimeWithoutTimezone(datetime_lib.datetime):
"""Datetime without timezone."""
@overload
def replace(
self,
year: SupportsIndex = ...,
month: SupportsIndex = ...,
day: SupportsIndex = ...,
hour: SupportsIndex = ...,
minute: SupportsIndex = ...,
second: SupportsIndex = ...,
microsecond: SupportsIndex = ...,
tzinfo: _TzInfo = ...,
*,
fold: int = ...,
) -> DatetimeWithTimezone: ...
@overload
def replace(
self,
year: SupportsIndex = ...,
month: SupportsIndex = ...,
day: SupportsIndex = ...,
hour: SupportsIndex = ...,
minute: SupportsIndex = ...,
second: SupportsIndex = ...,
microsecond: SupportsIndex = ...,
tzinfo: None = ...,
*,
fold: int = ...,
) -> Self: ...
@overload
def astimezone(self, tz: _TzInfo) -> DatetimeWithoutTimezone: ...
@overload
def astimezone(self, tz: None) -> Self: ...
def utcoffset(self) -> None: ...
def tzname(self) -> None: ...
def dst(self) -> None: ...
def __le__(self, value: DatetimeWithoutTimezone, /) -> bool: ... # type: ignore[override]
def __lt__(self, value: DatetimeWithoutTimezone, /) -> bool: ... # type: ignore[override]
def __ge__(self, value: DatetimeWithoutTimezone, /) -> bool: ... # type: ignore[override]
def __gt__(self, value: DatetimeWithoutTimezone, /) -> bool: ... # type: ignore[override]
@overload # type: ignore[override]
def __sub__(self, value: Self, /) -> timedelta: ...
@overload
def __sub__(self, value: timedelta, /) -> Self: ...
class datetime(datetime_lib.datetime):
@overload
def __new__(
cls,
year: SupportsIndex,
month: SupportsIndex,
day: SupportsIndex,
hour: SupportsIndex = ...,
minute: SupportsIndex = ...,
second: SupportsIndex = ...,
microsecond: SupportsIndex = ...,
tzinfo: _TzInfo = ...,
*,
fold: int = ...,
) -> DatetimeWithTimezone: ...
@overload
def __new__(
cls,
year: SupportsIndex,
month: SupportsIndex,
day: SupportsIndex,
hour: SupportsIndex = ...,
minute: SupportsIndex = ...,
second: SupportsIndex = ...,
microsecond: SupportsIndex = ...,
tzinfo: None = ...,
*,
fold: int = ...,
) -> DatetimeWithoutTimezone: ...
# On <3.12, the name of the first parameter in the pure-Python implementation
# didn't match the name in the C implementation,
# meaning it is only *safe* to pass it as a keyword argument on 3.12+
# Assume are on 3.12+
@overload
@classmethod
def fromtimestamp(
cls, timestamp: float, tz: None = ...
) -> DatetimeWithoutTimezone: ...
@overload
@classmethod
def fromtimestamp(
cls, timestamp: float, tz: _TzInfo
) -> DatetimeWithTimezone: ...
@overload
@classmethod
def now(cls, tz: _TzInfo) -> DatetimeWithTimezone: ...
@overload
@classmethod
def now(cls, tz: None = ...) -> DatetimeWithoutTimezone: ...
@overload
@classmethod
def combine(
cls, date: _Date, time: _Time, tzinfo: None = ...
) -> DatetimeWithoutTimezone: ...
@overload
@classmethod
def combine(
cls, date: _Date, time: _Time, tzinfo: _TzInfo
) -> DatetimeWithTimezone: ...
@classmethod
def strptime(
cls, date_string: str, format: str, /
) -> DatetimeWithTimezone | DatetimeWithoutTimezone: ...
I have some questions before I'm certain this could be possible for everyone
- Is it possible to make this backwards compatible?
- Is this something others are interested in?
- Should this actually be solved in the datetime library directly?