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Pydantic A URL field received an absolute URL when a relative URL was expected.
Understanding Pydantic and Its Purpose
Pydantic is a data validation and settings management library for Python, leveraging Python's type annotations. It is widely used for ensuring that data structures adhere to specified types and constraints, making it invaluable for applications that require strict data validation. Pydantic is particularly popular in web development, where it is often used to validate incoming JSON data in APIs.
Identifying the Symptom: value_error.url.absolute
When working with Pydantic, you might encounter the error code value_error.url.absolute. This error typically arises when a URL field in a Pydantic model is expected to receive a relative URL, but instead, an absolute URL is provided. This can lead to validation failures, preventing the application from processing the data correctly.
Explaining the Issue: Why Absolute vs. Relative URLs Matter
The error value_error.url.absolute indicates a mismatch between the expected and provided URL formats. In web applications, relative URLs are often used to refer to resources within the same domain, while absolute URLs include the full path, including the protocol and domain name. Pydantic's URL validation can be configured to accept only relative URLs for specific fields, ensuring that data conforms to the expected format.
Example Scenario
Consider a Pydantic model designed to accept relative URLs for internal API endpoints. If an absolute URL like https://example.com/api/resource is provided instead of a relative URL like /api/resource, the validation will fail, triggering the value_error.url.absolute error.
Steps to Fix the Issue
To resolve this issue, you need to ensure that the data provided to the Pydantic model matches the expected format. Here are the steps to fix the problem:
Step 1: Review the Pydantic Model
Check the Pydantic model definition to confirm that the URL field is configured to accept relative URLs. This is typically done using a custom validator or by specifying constraints in the field definition.
from pydantic import BaseModel, validator
from pydantic.networks import AnyUrl
class MyModel(BaseModel):
endpoint: AnyUrl
@validator('endpoint')
def check_relative_url(cls, v):
if v.is_absolute():
raise ValueError('Only relative URLs are allowed')
return v
Step 2: Modify the Input Data
Ensure that the data being passed to the model contains relative URLs. If you control the data source, update it to provide URLs in the correct format.
data = {
'endpoint': '/api/resource'
}
Step 3: Validate the Data
Re-run the data through the Pydantic model to ensure it passes validation without errors.
try:
model_instance = MyModel(**data)
print('Validation successful:', model_instance)
except ValueError as e:
print('Validation error:', e)
Additional Resources
For more information on Pydantic and URL validation, consider visiting the following resources:
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Pydantic A URL field received an absolute URL when a relative URL was expected.
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Pydantic A URL field received an absolute URL when a relative URL was expected.
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