Summary - Pydantic

Combine BaseModel, Field and validator to write a user validation model.

Summary - Pydantic

In this group you learned the core concepts of Pydantic. BaseModel for model definition, Field for validation rules, field_validator for custom validation, model_config for settings, model_validate for building a model from a dict.

class User(BaseModel):
    name: str = Field(min_length=2)
    age: int = Field(gt=0, lt=200)

    @field_validator("name")
    @classmethod
    def short(cls, v):
        return v

In the final step you will combine all of these to write a user validation model.

Exercise User validation model

Start with from pydantic import BaseModel, Field, field_validator. Define class User(BaseModel):. Add fields name: str = Field(min_length=2) and age: int = Field(gt=0, lt=200). With @field_validator("name") and @classmethod define def short(cls, v): that does return v. Create an instance with u = User(name="Ayşe", age=30). Print the values with print(u.name, u.age).

Show example solution

from pydantic import BaseModel, Field, field_validator

class User(BaseModel):
    name: str = Field(min_length=2)
    age: int = Field(gt=0, lt=200)

    @field_validator("name")
    @classmethod
    def short(cls, v):
        return v

u = User(name="Ayşe", age=30)
print(u.name, u.age)

Test yourself

Which one adds custom validation to a field?
- @field_validator
- BaseModel
- Field
- model_config
Show answer

@field_validator — @field_validator adds custom validation to a field.
Match the group tools

BaseModel

Model base
Field

Validation rule
field_validator

Custom validation
model_validate

Dict to model

Next lesson: Singleton

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