ValueError: View Function Did Not Return a Response
Armin Ronacher
—The Problem
Traceback (most recent call last): File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1836, in __call__ return self.wsgi_app(environ, start_response) File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1820, in wsgi_app response = self.make_response(self.handle_exception(e)) File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1403, in handle_exception reraise(exc_type, exc_value, tb) File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1817, in wsgi_app response = self.full_dispatch_request() File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1478, in full_dispatch_request response = self.make_response(rv) File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1566, in make_response raise ValueError('View function did not return a response') ValueError: View function did not return a response
The Solution
All Flask views must return a value, usually a Response object. If the flask view throwing the error accepts GET and POST methods, check if you are neglecting return a value for one of the cases.
@app.route('/', methods=['GET', 'POST']) def index(): if request.method == 'POST': model.save() # Failure to return a redirect or render_template else: return render_template('index.html')
Further Reading
If you’re looking to get a deeper understanding of how Flask application monitoring works, take a look at the following articles:
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- Listen to the Syntax Podcast
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