[FIXED] How to make pydantic class fields immutable?

Issue

I am trying to create a pydantic class with Immutable class fields (not instance fields).

Here is my base code:

from pydantic import BaseModel

class ImmutableModel(BaseModel):
    _name: str = "My Name"
    _age: int = 25

ImmutableModel._age = 26

print("Class variables:")
print(f"Name: {ImmutableModel._name}")
print(f"Age: {ImmutableModel._age}")

Output:

Class variables:
Name: My Name
Age: 26

I tried using the Config class inside my ImmutableModel to make fields immutable. But it seems like it only works for instance class fields.

class Config:
    allow_mutation = False

FYI, I use Python 3.6.13 and pydantic==1.9.2

Solution

Initially, I tried to achieve creating immutable Class and Instance using pydantic module.

Now I were able to manage it using native method itself. Since this was completely defined by me and immutable, its fine to have no validation.

class ImmutableMetaclass(type):
    
    def __setattr__(cls, name, value):
        raise AttributeError("Cannot create or set class attribute '{}'".format(name))

class MyImmutableClass(metaclass=ImmutableMetaclass):
    
    # Define all allowed class attributes here
    CONSTANT_1 = 1

    def __setattr__(self, name, value):
        raise AttributeError("Cannot create or set class or instance attribute '{}'".format(name))

immutable_class = MyImmutableClass
immutable_class.CONSTANT_1 = 100
immutable_class.CONSTANT_2 = 200

immutable_instance = MyImmutableClass()
immutable_instance.CONSTANT_1 = 100
immutable_instance.CONSTANT_3 = 300

All the above code raises AttributeError.

Answered By - arudsekaberne