Serializing Date parameters does not support allow_None #578
Description
Param: 1.12.0
I'm trying to help a user that wants to implement the Pydantic getting started example using Param. https://discourse.holoviz.org/t/creating-an-optional-datetime-parameter-using-param/3147.
He asks how to implement signup_ts: Optional[datetime] = None. I think its not possible with the existing parameters as I get the below error.
$ python 'script.py'
Traceback (most recent call last):
File "script.py", line 12, in <module>
deserialized_data = User.param.deserialize_parameters(json_data)
File "C:\repos\private\panel-ai\.venv\lib\site-packages\param\parameterized.py", line 2100, in deserialize_parameters
return serializer.deserialize_parameters(self_or_cls, serialization, subset=subset)
File "C:\repos\private\panel-ai\.venv\lib\site-packages\param\serializer.py", line 113, in deserialize_parameters
deserialized = pobj.param[name].deserialize(value)
File "C:\repos\private\panel-ai\.venv\lib\site-packages\param\__init__.py", line 1928, in deserialize
return dt.datetime.strptime(value, "%Y-%m-%dT%H:%M:%S.%f")
TypeError: strptime() argument 1 must be str, not Noneimport param
import json
class User(param.Parameterized):
signup_ts = param.Date(allow_None=True, doc="""The sign up time of the user""")
external_data = {
'signup_ts': None,
}
json_data = json.dumps(external_data)
deserialized_data = User.param.deserialize_parameters(json_data)
User(**deserialized_data)Additional Context
If you look at the Pydantic getting started example you will realize that its deserializing is much more flexible/ forgiving as it will be able to converts string to ints for integer parameters, not care so much about the date time format for datetime parameters etc.