Models
Pydantic Docs · docs.pydantic.dev [1]
I came accross from_attributes today it allows creation of pydantic models from objects such as a sqlalchemy Base Model or while nesting pydantic models. I believe in the past I have ran into some inconsistencies with nesting pydantic models and I’ll bet one had from_attributes set and another did not.
Arbitrary class instances¶
(Formerly known as “ORM Mode”/from_orm).
Pydantic models can also be created from arbitrary class instances by reading the instance > attributes corresponding to the model field names. One common application of this functionality is integration with object-relational mappings (ORMs).
To do this, set the from_attributes config value to True (see the documentation on Configuration for more details).
The example here uses SQLAlchemy, but the same approach should work for any ORM.
References:
[1]: https://docs.pydantic.dev/latest/concepts/models/#rebuilding-model-schema
Posts tagged: pydantic
All posts with the tag "pydantic"
3 posts
latest post 2025-01-28
Publishing rhythm
Fields
Pydantic Docs · docs.pydantic.dev [1]
exclude=True and repr=False is a good pydantic combination for secret attributes such as user passwords, or hashed passwords. exclude keeps it out of model_dumps, and repr keeps it out of the logs.
from pydantic import BaseModel, Field
class User(BaseModel):
name: str = Field(repr=True)
age: int = Field(repr=False)
user = User(name='John', age=42)
print(user)
#> name='John'
References:
[1]: https://docs.pydantic.dev/2.7/concepts/fields/#field-representation
External Link
stackoverflow.com [1]
I went down the route of leveraging the json-enc extention in htmx [2], but later realized that this completely breaks browsers/users who do not wish to use javascript. While most of the web would feel quite broken with javascript disabled, I don’t want to contribute to that without good reason.
Taking a second look into this issue, rather than using json-enc, and using as_form to get form data into a model keeps the nice DX fo everything being a pydantic model, but the site still works without js. with js htmx kicks in, you get a spa like experience by loading partials onto the page, and without, you just get a full page reload.
the implementation # [3]
copied from https://stackoverflow.com/questions/60127234/how-to-use-a-pydantic-model-with-form-data-in-fastapi
import inspect
from typing import Type
from fastapi import Form
from pydantic import BaseModel
from pydantic.fields import ModelField
def as_form(cls: Type[BaseModel]):
new_parameters = []
for field_name, model_field in cls.__fields__.items():
model_field: ModelField # type: ignore
new_parameters.append(
inspect.Parameter(
model_field.alias,
inspect.Parameter.POSITION...
global Field
global BaseModel
from pydantic import BaseModel
from pydantic import Field
Pydantic is a Python library for serializing data into models that can be validated with a deep set of built in valitators or your own custom validators, and deserialize back to JSON or dictionary.
Installation #
To install pydantic you will first need python and pip. Once you have pip installed you can install pydantic with pip.
pip install pydantic
Always install in a virtual environment
Creating a Pydantic model #
To get started with pydantic you will first need to create a Pydantic model.
This is a python class that inherits from pydantic.BaseModel.
from pydantic import BaseModel
from pydantic import Field
from typing import Optional
class Person(BaseModel):
name: str = Field(...)
age: int
parsing an object #
person = Person(name="John Doe", age=30)
print(person)
name='John Doe' age=30
data serialization #
Pydantic has some very robust serialization methods that will automatically coherse your data into the type specified by the type-hint in the model if it can.
person = Person(name=12, age="30")
print(f'name: {person.name}, type: {type(person.name)}')
print(f'age: {person.age}, type: {type(person.age)}')
1 validation error for Person
name
Input should be a valid string [type=string_type, input_value=12, input_type=int]
For further information visit https://errors.pydantic.dev/2.3/v/string_type
person = Person(name="John Doe", age='thirty')
print(f'name: {person.name}, type: {type(person.name)}')
print(f'age: {person.age}, type: {type(person.age)}')
1 validation error for Person
age
Input should be a valid integer, unable to parse string as an integer [type=int_parsing, input_value='thirty', input_type=str]
For further information visit https://errors.pydantic.dev/2.3/v/int_parsing