repr(TzInfo(0)) returns invalid python code

[15r10nk]

Hi, I'm the author of inline-snapshot and have a problem with the way TzInfo.__repr__ is implemented.

TzInfo has currently the following repr:

from pydantic_core import TzInfo

def test_TzInfo():
    assert repr(TzInfo(0)) == 'TzInfo(UTC)'
    assert repr(TzInfo(1)) == 'TzInfo(+00:00:01)'
    assert repr(TzInfo(5000)) == 'TzInfo(+01:23:20)'

The problem is that inline-snapshot uses by default repr() to generate the python code for the snapshots.

from pydantic_core import TzInfo
import datetime
from inline_snapshot import snapshot


def test_TzInfo():
    assert datetime.datetime(1, 2, 3, tzinfo=TzInfo(0)) == snapshot(
        datetime.datetime(1, 2, 3, 0, 0, tzinfo=TzInfo(UTC))
    )

inline-snapshot users then try to import UTC from somewhere which causes other problems.

Is it possible to change the repr() result of TzInfo to the following (add "").

from pydantic_core import TzInfo

def test_TzInfo():
    assert repr(TzInfo(0)) == 'TzInfo("UTC")'
    assert repr(TzInfo(1)) == 'TzInfo("+00:00:01")'
    assert repr(TzInfo(5000)) == 'TzInfo("+01:23:20")'

And to provide the possibility for TzInfo to be constructed from a string?

This should make

assert eval(repr(tzinfo)) == tzinfo

work for all TzInfo objects.

[Viicos]

I think it makes sense to add quotes in the repr so I went and created #1701. However, I'm not sure inline-snapshot is taking a robust approach here by assuming eval(repr(obj)) works for any obj. In the case of TzInfo, TzInfo("UTC") (or any kind of non-integer argument) fails, and there's no unspoken rule that I know of stating that the evaluation of Python objects representations should result in the same object being re-created.

[alexmojaki]

there's no unspoken rule that I know of stating that the evaluation of Python objects representations should result in the same object being re-created.

From https://docs.python.org/3/library/functions.html#repr:

For many types, this function makes an attempt to return a string that would yield an object with the same value when passed to eval()

From https://docs.python.org/3/reference/datamodel.html#object.__repr__:

If at all possible, this should look like a valid Python expression that could be used to recreate an object with the same value (given an appropriate environment)

[Viicos]

Ah then TIL. I think we can make it so that __str__() returns "UTC"/"+00:00:01", and __repr__() returns TzInfo(0/1/...).

[15r10nk]

Ah then TIL. I think we can make it so that __str__() returns "UTC"/"+00:00:01", and __repr__() returns TzInfo(0/1/...).

This would also be ok for me. But I think that an hour offset would then be a multiple of 60.