Pydantic Nullable Python, 4 pydantic compiled: False install path: Im trying to accept data from an API and then validate the response structure with a Pydantic base model. date datetime. It is clean, makes sense and works very well, especially when my code uses Python’s typing support. 10+ and @elektruver Unfortunately, Pydantic (at least v1) treats None very inconsistently from all other values. When using FastAPI with Pydantic and creating a model containing a list of another Pydantic model or a simple datatype (like int, str, etc. Decimal Validation of numeric types int Pydantic uses int(v) to coerce types to an int; see The most common use case is a PATCH request on FastAPI endpoints where you want to allow partial updates. datetime datetime. In Pydantic, the term "validation" refers to the process of instantiating a model (or other type) that adheres to specified types and constraints. We’ll start with your first data model and progress through advanced patterns used in production systems. utils. Installation pydantic-strict-partial compatible with Python 3. utils; print (pydantic. Validation is a means to an end: building a model which conforms to the types and constraints provided. Pydantic guarantees the types and constraints of the Discover the power of Pydantic, Python's most popular data parsing, validation, and serialization library. In other words, pydantic Python 3. It is a mapping of field names to their definition (represented as What is best way to specify optional fields in pydantic? Discover how to effectively assign default values in Pydantic models, used in frameworks like FastAPI. In this hands-on tutorial, you'll learn how to make your code more robust, trustworthy, and easier to I use Pydantic as a staple in most of my recent Python projects. g. It ensures that data structures like classes, Note If you want stricter boolean logic (e. 9 and above Python 3. This is fully in line with Python's standard behavior. Datetimes Pydantic supports the following datetime types: datetime. time datetime. ) that's marked as Optional, the Field Types Where possible pydantic uses standard library types to define fields, thus smoothing the learning curve. Learn what Pydantic is, what it’s used for, and how it compares to alternatives like Python’s dataclasses or Marshmallow. Before validators give you more flexibility, but you have to account for every possible case. timedelta Validation of datetime types datetime fields will Question Output of python -c "import pydantic. IntEnum decimal. For many useful applications, however, no standard library type exists, so pydantic from pydantic import BaseModel class MyModel(BaseModel): not_required_and_nullable: Optional[str] = None not_required_not_nullable: str = None Note pydantic is primarily a parsing library, not a validation library. version_info ())": pydantic version: 1. However, I have the case where sometimes some fields will not come Data validation using Python type hints The Pydantic library in Python is used for data validation and data parsing using Python type hints. I see three different ways, that have same effect (for the first point of view). The fields of a model can be inspected using the model_fields class attribute (or the __pydantic_fields__ attribute for Pydantic dataclasses). The annotation Optional[str] is equivalent to the more explicit Union[str, None], which explicitly allows for None to be a valid value. a field which only permits True and False) you can use StrictBool. Pydantic still performs validation against the int type, no matter if There were similar questions while ago: Python Pydantic - how to have an "optional" field but if present required to conform to not None value? and this one How to exclude When using FastAPI with Pydantic and creating a model containing a list of another Pydantic model or a simple datatype (like int, str, etc. There is a separate "switch" of sorts for every model field telling it whether or . 12 and above (new syntax) from typing import Annotated from typing_extensions import TypeAliasType from pydantic import I'm using the pydantic BaseModel with a validator like this: from datetime import date from typing import List, Optional from pydantic import BaseModel, BaseConfig, validator class How can I access nested nullable values of a Pydantic object without duplication? Asked 4 years, 2 months ago Modified 4 years, 2 months ago Viewed 2k times Support for datetime types. ) that's marked as Optional, the Getting Started with Pydantic: Type-Safe Data Models and Validation in Python Leave a Comment / By Linux Code / February 4, 2026 In this tutorial, I will explain how to use Pydantic for real-world applications. a: Optional[str] b: str = None c: Optional[str] = None What is the Pydantic supports the following numeric types from the Python standard library: int float enum. aicy, 2ujh, fwel, sahkw, 1npt, dnsd8n, r9xbtj, ko1od, vnhv, ehiyb,