assertionerror: .accepted_renderer not set on response
An AssertionError with the message “.accepted_renderer not set on response” occurs when the accepted_renderer attribute is not set on a response object in the context of a web application.
When handling a request in a web application, the server generates a response that will be sent back to the client. The accepted_renderer attribute is responsible for determining the format in which the response should be rendered. This attribute should be set on the response object to indicate the preferred content type – such as HTML, JSON, XML, etc.
Example
Let’s consider a simple example in Python, using the Flask web framework:
from flask import Flask, jsonify
app = Flask(__name__)
@app.route('/data')
def get_data():
response = jsonify({'message': 'Data retrieved successfully'})
# response.accepted_renderer = 'json' # Uncomment this line to avoid the AssertionError
return response
if __name__ == '__main__':
app.run()In this example, we have a Flask application with a single route defined at the “/data” endpoint. When a GET request is made to this endpoint, the get_data() function is executed. Inside this function, we create a JSON response using the jsonify function provided by Flask.
However, as the accepted_renderer attribute is not set on the response object, an AssertionError will be raised when returning the response to the client.
To resolve this error, we need to set the accepted_renderer attribute on the response object. Uncommenting the line response.accepted_renderer = 'json' in the code snippet above will set the renderer to JSON and prevent the AssertionError from occurring.