input is too short validating a datetime when month and day are not zero padded, but dash delimited

[akrherz]

Initial Checks

• I confirm that I'm using Pydantic V2

Description

IMHO, the provision of a date with dashes and without zero padded month, day values, is valid. python strptime allows this. I agree that this is ambiguous when no dashes are provided.

Example Code

from datetime import datetime
from pydantic import BaseModel, Field

class MyModel(BaseModel):
    dt: datetime = Field(...)

print(datetime.strptime("2024-4-5", "%Y-%m-%d"))
print(MyModel(dt="2024-4-5"))

2024-04-05 00:00:00
Traceback (most recent call last):
  File "/tmp/example.py", line 10, in <module>
    print(MyModel(dt="2024-4-5"))
          ^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/miniconda3/envs/prod/lib/python3.11/site-packages/pydantic/main.py", line 171, in __init__
    self.__pydantic_validator__.validate_python(data, self_instance=self)
pydantic_core._pydantic_core.ValidationError: 1 validation error for MyModel
dt
  Input should be a valid datetime or date, input is too short [type=datetime_from_date_parsing, input_value='2024-4-5', input_type=str]
    For further information visit https://errors.pydantic.dev/2.6/v/datetime_from_date_parsing

Python, Pydantic & OS Version

pydantic version: 2.6.4
        pydantic-core version: 2.16.3
          pydantic-core build: profile=release pgo=false
                 install path: /opt/miniconda3/envs/prod/lib/python3.11/site-packages/pydantic
               python version: 3.11.9 | packaged by conda-forge | (main, Apr 19 2024, 18:36:13) [GCC 12.3.0]
                     platform: Linux-5.14.0-437.el9.x86_64-x86_64-with-glibc2.34
             related packages: typing_extensions-4.11.0 fastapi-0.110.2
                       commit: unknown

Note, I am stuck on an old version awaiting a release with #9227 fixed. My apologies if this issue does not exist with the current release :(

[akrherz]

Just denoting that this issue still exists on 2.7.1 as I can upgrade to it now :)

[sydney-runkle]

@akrherz,

Thanks for the report! Just to clarify - I believe #9227 has been resolved with 2.7.1 - please open a new issue if you're still experiencing problems in that regard!

Regarding your proposed change, I think that would have to wait until V3. Our docs do explicitly state that said type is not allowed, even in lax mode: https://docs.pydantic.dev/latest/api/standard_library_types/#datetimedatetime.

Closing for now, as I don't think this is a change we're likely to make, given that the desired behavior can easily be achieved with a custom validator. That being said, if this issue gets a bunch of traction / support, we could certainly consider for V3.