In Pydantic, how do I apply the flags that I have set in my base model to my custom type?
In my model, I have fields that are mandatory. Users try to avoid filling in these fields by using a dash character (-) as input. To avoid this from happening, I wrote a custom string type in Pydantic. The custom type checks if the input should change to None and checks if it is allowed to be None. The problem that I have is that my custom type does not use the Flags of my BaseModel. Such as anystr_strip_whitespace, to remove the whitespace from the beginning and end of the string. I would like to have the Config from the BaseModel also applied in my custom types. Therefore I hope that anybody can help me with my question about applying the flags of the BaseModel in a custom type.
All help is appreciated
Some example code:
class MyBaseModel(BaseModel): class Config: anystr_strip_whitespace = True class EmptyStrToNone(str): @classmethod def __get_validators__(cls): yield cls.change_empty_string_to_none @classmethod def change_empty_string_to_none(cls, value: str, field: ModelField) -> Optional[str]: """If the field is Optional, the input which represents an empty string is set to None. If the field is required, instead of returning None it raises an Exception.""" is_required = field.required lowercase_value = str(value).lower() if is_required: # Faulty cases that raise an exception # E.g. check in a dictionary if it has a string such as "not specified" that represents an empty string. elif # Optional condition return None return str_validator(value)
You can receive the
configand use it to decide if the
strshould be stripped. From Validators - pydantic:
A few things to note on validators:
you can also add any subset of the following arguments to the signature (the names must match):
config: the model config
from pydantic import BaseConfig, BaseModel from pydantic.validators import str_validator class MyStr(str): @classmethod def __get_validators__(cls): yield str_validator yield cls._strip_whitespace # Yield more custom validators if needed @classmethod def _strip_whitespace(cls, value: str, config: BaseConfig) -> str: if config.anystr_strip_whitespace: return value.strip() return value class MyBaseModel(BaseModel): my_str: MyStr class Config: anystr_strip_whitespace = True print(MyBaseModel(my_str=" a "))