title: Python Flask ValueError: View function did not return a response
body: <p>This is my Flask code:</p>
  
  <pre><code>from flask import Flask
  from flask import request
  
  app = Flask(__name__)
  
  @app.route('/', methods=['GET', 'POST'])
  def signal():
      if request.method == 'POST':
          content = request.get_json()
          return content
      else:
          return 'Hello, world!'
  
  if __name__ == '__main__':
      app.run(debug=True)
  </code></pre>
  
  <p>I run this HTTP Post (from the same machine):</p>
  
  <pre><code>import requests
  import json
  dump= '{"on":"true"}'
  r = requests.post('http://127.0.0.1:5000', dump)
  </code></pre>
  
  <p>And receive this error:</p>
  
  <pre><code>[2017-03-04 14:18:35,250] ERROR in app: Exception on / [POST]
  Traceback (most recent call last):
  File "c:\users\andrew\appdata\local\programs\python\python35-32\lib\site-packages\flask\app.py", line 1982, in wsgi_app
  response = self.full_dispatch_request()
  File "c:\users\andrew\appdata\local\programs\python\python35-32\lib\site-packages\flask\app.py", line 1615, in full_dispatch_request
  return self.finalize_request(rv)
  File "c:\users\andrew\appdata\local\programs\python\python35-32\lib\site-packages\flask\app.py", line 1630, in finalize_request
  response = self.make_response(rv)
  File "c:\users\andrew\appdata\local\programs\python\python35-32\lib\site-packages\flask\app.py", line 1725, in make_response
  raise ValueError('View function did not return a response')
  ValueError: View function did not return a response
  </code></pre>
  
  <p>Any ideas on why this is occuring? From reading online at first I thought it was because I didn't have an else in case of it being a GET, but I can't understand now.</p>