Type for not allowing NUL characters in strings

[Spaxterr]

Hello, I would like a type for my models that validates strings and makes sure they are not empty and do not contain any NUL (\0) characters. The closest I've gotten is Field(min_length=1, strip_whitespace=True, pattern='[^\0]+'). However I'd like to bundle this into a type rather than using Field on every attribute.

I'd like something like this if possible:

class MyModel(BaseModel)
    value: NonEmptyString  # Checks for empty and NUL characters

[ybressler]

You can use a constrained string:

from pydantic import constr
NonEmptyString = constr(strip_whitespace=True, min_length=1, pattern='[^\0]+')

Alternatively, if you want more control, you can use an annotated validator:

from pydantic.functional_validators import AfterValidator

def do_something(v: str) -> str:
    if "something" in v:
        raise ValueError()
    return v

NonEmptyString = Annotated[
    constr(strip_whitespace=True, min_length=1, pattern='[^\0]+'),
    AfterValidator(do_something)
]