Multipage app trouble after updating dash components


Hi! i’m using gunicorn to serve multi page app. After updating all dash packages i faced that error:

Traceback (most recent call last):
File “/home/roman/analitic_app/lib/python3.5/site-packages/flask/”, line 1982, in wsgi_app
response = self.full_dispatch_request()
File “/home/roman/analitic_app/lib/python3.5/site-packages/flask/”, line 1607, in full_dispatch_request
File “/home/roman/analitic_app/lib/python3.5/site-packages/flask/”, line 1654, in try_trigger_before_first_request_functions
File “/home/roman/analitic_app/lib/python3.5/site-packages/dash/”, line 544, in _setup_server
File “/home/roman/analitic_app/lib/python3.5/site-packages/dash/”, line 234, in _generate_scripts_html
self.scripts.get_all_scripts() +
File “/home/roman/analitic_app/lib/python3.5/site-packages/dash/”, line 123, in get_all_scripts
return self._resources.get_all_resources()
File “/home/roman/analitic_app/lib/python3.5/site-packages/dash/”, line 56, in get_all_resources
self.get_inferred_resources() + self._resources
File “/home/roman/analitic_app/lib/python3.5/site-packages/dash/”, line 84, in get_inferred_resources
for t in layout.traverse():
AttributeError: ‘NoneType’ object has no attribute ‘traverse’

and in browser

have no idea why app stoped working. i have read dash’s update notes on github and remove secret key from but it didnt help. am i the only one facing that trouble?


Hey @roman - I’m not sure what’s going on here, but this error message has to do with app.layout. For some reason, the app thinks that it is None.


Hey @roman did you find a solution? I’m having the same problem…


Yes. That was my fail =) I forgot correct command to run app with gunicorn. In two words i typed gunicorn -b -w 4 index:app instead gunicorn -b -w 4 index:app.server


THANK YOU! Just have to say I was going crazy with this same issue. Simply changing app:server to index:app.server in the Procfile fixed this.