Chaining validators

It is possible to combine validators together. There’s a few ways to do this, I’ll go over them below.

pankoff.combinator.combine(*validators, **kwargs)

Returns either “raw” combined validator or an instance of it.

Parameters

• validators – Validators to combine

• kwargs – If specified, kwargs will be unpacked to newly created combined validator

Returns

Either “raw” combined validator or its instance

Using combine() function

combine() allows you to do exactly 2 things, create “raw” combined validator, or create combined “instance”.

Lets create “raw” combined validator first:

from pankoff.magic import autoinit
from pankoff.combinator import combine
from pankoff.validators import String, Sized

sized_name = combine(String, Sized)

Now, we can actually use it to create instances:

@autoinit
class Person:
    name = sized_name(min_size=5)

guido = Person(name="Guido")
print(guido.name)  # Guido

Alternatively, you can create instance straight away:

@autoinit
class Person:
    name = combine(String, Sized, min_size=5)

guido = Person(name="Guido")
print(guido.name)  # Guido

Using “and” operator

Besides combine() function, you can chain validators using & operator, it’ll create a “raw” validator for you:

>>> raw_validator = Sized & String & Number & Type
>>> raw_validator
Combination of (Sized, String, Number, Type) validators
>>> validator = raw_validator(...)
>>> validator
CombinedValidator(Sized, String, Number, Type)

Using inheritance

Chaining uses inheritance mechanism under the hood, so you can do the following:

class MyCombinedValidator(String, Sized, ...):
    pass