# Fix Flask ValueError View Function Did Not Return a Response

> Ensure every Flask view function returns a value for all code paths, including both GET and POST handlers, to avoid the ValueError on missing responses

**URL:** https://sentry.io/answers/valueerror-view-function-did-not-return-a-response/

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## The Problem

```python
Traceback (most recent call last):
  File "/usr/local/lib/python3/site-packages/flask/app.py", line 1836, in __call__
    return self.wsgi_app(environ, start_response)
  File "/usr/local/lib/python3/site-packages/flask/app.py", line 1820, in wsgi_app
    response = self.make_response(self.handle_exception(e))
  File "/usr/local/lib/python3/site-packages/flask/app.py", line 1403, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/usr/local/lib/python3/site-packages/flask/app.py", line 1817, in wsgi_app
    response = self.full_dispatch_request()
  File "/usr/local/lib/python3/site-packages/flask/app.py", line 1478, in full_dispatch_request
    response = self.make_response(rv)
  File "/usr/local/lib/python3/site-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](https://flask.palletsprojects.com/en/stable/api/#response-objects). 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.

```python
@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:

- [Building a SaaS application block by block](https://blog.sentry.io/how-to-build-saas-application/)
- [How slow is slow?](https://blog.sentry.io/how-slow-is-slow/)
- [Getting started with the Flask SDK (docs)](https://docs.sentry.io/platforms/python/integrations/flask/)

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*Source: [sentry.io/answers/valueerror-view-function-did-not-return-a-response/](https://sentry.io/answers/valueerror-view-function-did-not-return-a-response/)*