Pydantic Enum Class Validator

What will you learn?

Learn how to use Pydantic to validate enum classes in Python and implement enum validation for data models using Pydantic.

Introduction to the Problem and Solution

In this tutorial, we delve into harnessing the robust data validation capabilities of Pydantic by focusing on validating Enum classes. When dealing with intricate data structures or APIs, ensuring specific fields conform to a predefined set of values is pivotal. By leveraging Pydantic, a versatile data validation library, we can effortlessly enforce these constraints within our Python applications.

To accomplish this, we’ll define an Enum class that represents acceptable values for a particular field in our data model. By integrating this Enum class with a Pydantic model definition, we can seamlessly validate incoming data against these predetermined options.


Demonstration of using Pydantic for validating an Enum class:

from pydantic import BaseModel
from enum import Enum

class StatusEnum(str, Enum):
    active = "active"
    inactive = "inactive"
    pending = "pending"

class Item(BaseModel):
    name: str
    status: StatusEnum

# Usage example:
item_data = {"name": "Test Item", "status": "active"}
validated_item = Item(**item_data)

# Copyright PHD


In the provided code snippet: 1. Define an StatusEnum class inheriting from both str and Enum, specifying valid choices for the status field. 2. Create a subclass named Item under BaseModel, containing attributes for name (a string) and status (an instance of our defined StatusEnum). 3. Validate input data against our model schema by instantiating an Item object with sample data. 4. If input does not match the expected format or values defined by our Enum class (StatusEnum), Pydantic raises appropriate validation errors.

  1. How do I add new options to my existing StatusEnum?

  2. You can extend your existing StatusEnum by simply adding new members like so:

  3. class StatusEnum(str, Enum):
        active = "active"
        inactive = "inactive"
        pending = "pending"
  4. new_option = "new_option"
  5. # Copyright PHD
  6. Can I have duplicate values within my StatusEnum?

  7. No, each value within an Enum must be unique; duplicates are not allowed.

  8. Are Enums only restricted to string types?

  9. No, while strings are commonly used as enum values due to their readability, Enums in Python can represent any hashable type.

  10. Is it possible to iterate over all members of an Enum class?

  11. Yes! You can access all members using either list(StatusEnum) or iterating directly over StatusEnu

  12. Can I compare different enums together?

  13. Enums cannot be compared across different enumeration classes since they are distinct types

  14. What happens if invalid status is passed during object initialization?

  15. When initializing an object with invalid status value not present in your specified enum list then it would raise ValidationError


In conclusion, we’ve explored how Pydantic simplifies the process of validating enum classes within Python applications. By combining Enums with Pydantic’s BaseModel, you can ensure strict adherence to predefined sets of permissible values throughout your projects.

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