Validating Pydantic field while setting value

Question

A Pydantic class that has confloat field cannot be initialised if the value provided for it is outside specified range. But when setting this field at later stage (my_object.constrained_field = <big_value>) the new value is not validated.

from pydantic import BaseModel, confloat

class testClass(BaseModel):
    a: confloat(gt=0.0, lt=10.0)

x = testClass(a=2.0) # OK

# x = testClass(a=20.0) # ERROR: outside limits

x.a = 40.0 # OK despite outside limits

print(x.a) # prints '40.0'

Is this possible to validate new value when setting member, so that calling x.a = 40.0 in the example above will raise an exception?

If not -is there any workaround like getting validator method out of the class field?

score 12 · Accepted Answer · answered Jul 03 '20 at 14:32

12

Use validate_assignment on Config.

answered Jul 03 '20 at 14:32

SColvin

11,584
6
57
71

Do you see any reason why `validate_assignment` is not `True` by default? – MaciekS Dec 04 '20 at 08:48
It has a performance impact and I would argue that the majority of cases wouldn't expect it to be on by default. – SColvin Dec 04 '20 at 12:27
1

curious- does this cause root validators to be re-triggered? – karuhanga Jan 31 '22 at 18:13

Validating Pydantic field while setting value

1 Answers1