Dash does not properly work with library called jupyter_dash [BUG]

[arani-mohammad]

Thank you for providing this fantastic library.
I had a problem dash/jupyter_dash that I copied below.

dash                      2.1.0
dash-bootstrap-components 1.0.2
dash-core-components      2.0.0
dash-html-components      2.0.0
dash-renderer             1.1.2
dash-table                5.0.0
jupyter-dash              0.4.0

---

AttributeError Traceback (most recent call last)
/var/folders/xv/d091l2wd693b381xlqk8r1500000gn/T/ipykernel_5375/385882412.py in
50
51 if name == "main":
---> 52 app.run_server(mode = "external", debug=True, port=8050)
53 # app.run_server(debug=True, mode='inline',host="0.0.0.0",port=8058)

~/opt/anaconda3/envs/DPWorld2_conda_install_only/lib/python3.8/site-packages/jupyter_dash/jupyter_app.py in run_server(self, mode, width, height, inline_exceptions, **kwargs)
229 else:
230 requests_pathname_prefix = '/'
--> 231 self.config.update({'requests_pathname_prefix': requests_pathname_prefix})
232
233 # Compute server_url url

~/opt/anaconda3/envs/DPWorld2_conda_install_only/lib/python3.8/site-packages/dash/_utils.py in update(self, other)
167 # Overrides dict.update() to use setitem above
168 for k, v in other.items():
--> 169 self[k] = v
170
171 # pylint: disable=inconsistent-return-statements

~/opt/anaconda3/envs/DPWorld2_conda_install_only/lib/python3.8/site-packages/dash/_utils.py in setitem(self, key, val)
156 def setitem(self, key, val):
157 if key in self.dict.get("_read_only", {}):
--> 158 raise AttributeError(self._read_only[key], key)
159
160 final_msg = self.dict.get("_final")

AttributeError: ('Read-only: can only be set in the Dash constructor or during init_app()', 'requests_pathname_prefix')

[kaburelabs]

Same error here

[cogerk]

I'm also experiencing this error in a jupyter notebook without jupyter_dash, here's my notebook (scrubbed domain name for privacy):

import dash
from dash import dcc
from dash import html
import pandas as pd
import plotly.express as px
import dash_bootstrap_components as dbc

#NOTE: reload the whole app code if altering the callbacks, else the UI can bug out
app_port = 88900



#flask is default if nothing set
import flask
server = flask.Flask(__name__)

app = dash.Dash(__name__, server=server, external_stylesheets=[dbc.themes.BOOTSTRAP])
server = app.server


#Demo App
#--------

# assume you have a "long-form" data frame
# see https://plotly.com/python/px-arguments/ for more options
df = pd.DataFrame({
    "Fruit": ["Apples", "Oranges", "Bananas", "Apples", "Oranges", "Bananas"],
    "Amount": [4, 1, 2, 2, 4, 5],
    "City": ["SF", "SF", "SF", "Montreal", "Montreal", "Montreal"]
})

fig = px.bar(df, x="Fruit", y="Amount", color="City", barmode="group")

app.layout = html.Div(children=[
    html.H1(children='Hello Dash'),

    html.Div(children='''
        Dash: A web application framework for your data.
    '''),

    dcc.Graph(
        id='example-graph',
        figure=fig
    )
])

from multiprocessing import Process
from IPython.display import IFrame
    

class Dash_jhub_app:

    # instance attribute
    def __init__(self,app):
        self.app = app
    
    def _render_app(self):
        self.app.config.update({
            # remove the default of '/'
            'requests_pathname_prefix': f'{self.port}/'
        })
        
        self.app.run_server(port=self.port,debug=self.debug) 
        
    def start(self,port,debug=True):
        self.port = port
        self.debug = debug
        self.thread= Process(target=self._render_app) #args=(self.app,self.port)
        self.thread.start()
    
    def url(self,user,url='https://jhub.DOMAIN.local/user/'):
        self.user = user
        self.url = f'{url}{self.user}/proxy/{self.port}'
        print(f'visit app at: {self.url}')  
        
    def show(self,color="white" ):
        return IFrame(self.url, width='100%', height='600px',allowtransparency="true",style=f"background-color: {color};" ) 
        
    def stop(self):
        self.thread.terminate()

_app = Dash_jhub_app(app)

_app.start(app_port) 
_app.url(user='cogert')

visit app at: https://jhub.DOMAIN.local/user/cogert/proxy/88900


Process Process-1:
Traceback (most recent call last):
  File "/opt/conda/lib/python3.7/multiprocessing/process.py", line 297, in _bootstrap
    self.run()
  File "/opt/conda/lib/python3.7/multiprocessing/process.py", line 99, in run
    self._target(*self._args, **self._kwargs)
  File "/tmp/ipykernel_1494/2485764532.py", line 14, in _render_app
    'requests_pathname_prefix': f'{self.port}/'
  File "/opt/conda/lib/python3.7/site-packages/dash/_utils.py", line 169, in update
    self[k] = v
  File "/opt/conda/lib/python3.7/site-packages/dash/_utils.py", line 158, in __setitem__
    raise AttributeError(self._read_only[key], key)
AttributeError: ('Read-only: can only be set in the Dash constructor or during init_app()', 'requests_pathname_prefix')

! pip freeze | grep dash

dash==2.1.0
dash-bootstrap-components==1.0.2
dash-core-components==2.0.0
dash-html-components==2.0.0
dash-table==5.0.0

_app.stop()

[jamescw]

Same here and the jupyter_dash lib has not seen a commit in a long time!

[alexcjohnson]

jupyter_dash hasn't had a commit in a long time because it's a thin wrapper around regular dash - it does what it needs to do and updates to dash just work with it. Until this update 🙃

We're working on a fix, but in the meantime, add this before your app.run_server call and it'll work with Dash 2.1:

del app.config._read_only["requests_pathname_prefix"]

Main issue: plotly/jupyter-dash#75

[jamescw]

Great thanks @alexcjohnson!

[alexcjohnson]

Fixed in jupyter-dash==0.4.1