Overwrite method on Pydantic instance

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There are many solutions available to overwrite methods on instances. But for an object of the pydantic BaseModel this seems to be problematic. This is a simple example:

from pydantic import BaseModel

class Dog(BaseModel):
    def bark(self):
        print("WOOF")

def new_bark():
    print("WoOoOoF!!")

Running the method:

>>> boby = Dog()
>>> boby.bark()
WOOF

Overwriting the method:

>>> boby.bark = new_bark
>>> boby.bark()
ValueError: "Dog" object has no field "bark"

The expected result would be a printed # WoOoOoF!!. If Dog does not inherit pydantics BaseModel you get the expected result.

Is this even possible?

pydantic python
1 Answers

I think the issue is somehow related with pydantic's __setattr__ method. It is some how different than normal objects. In this link, people deal with (not same but similar) issue. https://github.com/samuelcolvin/pydantic/issues/655

I don't know the internal details of pydantic or the cause of the issue, but I think this code would solve your problem:

>>> object.__setattr__(boby, "bark", new_bark)
>>> boby.bark()
WoOoOoF!!
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