# dash.exceptions.InvalidCallbackReturnValue

**URL:** <https://community.plotly.com/t/dash-exceptions-invalidcallbackreturnvalue/38937>\
**Category:** Dash Python\
**Created:** [May 5, 2020, 3:10pm UTC](https://community.plotly.com/t/dash-exceptions-invalidcallbackreturnvalue/38937 "2020-05-05T15:10:06Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![juanCarHer](https://avatars.discourse-cdn.com/v4/letter/j/35a633/32.png) [@juanCarHer](https://community.plotly.com/u/juanCarHer)\
**Post date:** [May 5, 2020, 3:10pm UTC](https://community.plotly.com/t/dash-exceptions-invalidcallbackreturnvalue/38937/1 "2020-05-05T15:10:06Z")

</div>

Hello!  
I’m having issues when I try running this code.  
I get this error

```auto
dash.exceptions.InvalidCallbackReturnValue: 
The callback for property `children`
of component `page-content` returned a value
which is not JSON serializable.

In general, Dash properties can only be
dash components, strings, dictionaries, numbers, None,
or lists of those.

```

I’m also getting another error related to PIL

```auto
AttributeError: module 'PIL.Image' has no attribute 'Image'

```

My code is like this

```auto
import dash
import dash_cytoscape as cyto
import dash_core_components as dcc
import dash_html_components as html
import dash_reusable_components as drc
import dash_bootstrap_components as dbc
from dash.dependencies import Input, Output, State

import networkx as nx
import community

import plotly.graph_objects as go

from datetime import datetime as dt
from random import randint
from itertools import islice
from matplotlib.colors import is_color_like

import pandas as pd
import numpy as np
import re
import textwrap
import itertools

app = dash.Dash(external_stylesheets=[dbc.themes.BOOTSTRAP])
app.config.suppress_callback_exceptions = True

navBar = dbc.NavbarSimple(
			children=[
				dbc.DropdownMenu(
					children=[
						dbc.DropdownMenuItem("Más Páginas", header=True),
						dbc.DropdownMenuItem("Panel de Control", href="/panelControl"),
						dbc.DropdownMenuItem("Animación", href="/nodosAnimacion")
						],
					nav=True,
					in_navbar=True,
					label="Más",
					),
				],
			brand="Banco Santander Análisis de Palabras",
			brand_href="/panelControl",
			color="primary",
			dark=True
			)

cardControlPanel = dbc.Card(
	[
		dbc.FormGroup(
			[
			drc.NamedDropdown(
				name="Layout", 
				id="dropdown-layout",
				options=drc.DropdownOptionsList(
					"grid", 
					"circle", 
					"concentric",
					"breadthfirst", 
					"cose"),
				value="cose", 
				clearable=False)
			]
		),
		dbc.FormGroup(
			[
			drc.NamedDropdown(
				name="Category",
				id="category", 
				options=drc.DropdownOptionsList(
					"Promotor",
					"Detractor",
					"Neutro"),
				value="Promotor",
				clearable=False,
				style={"width", "90%"})
			]
		),
		dbc.FormGroup(
			[
			drc.NamedSlider(
				name="Numero de Nodos",
				id="nodes-number",
				min=10,
				max=30,
				step=2,
				value=10,
				marks={value:str(value) for value in range(10, 31, 2)})
			]
		),
		dbc.FormGroup(
			[
			drc.NamedInput(
				name="Search", 
				id="input-box-word",
				type="text"),
			html.Button(
				"Submit",
				id="button-submit"),
			html.Button(
				"Clear",
				id="button-clear")
			]
		)

	],
	body=True
)

layoutControlPanel = dbc.Container(
	[
		html.H1("Panel de Control"),
		html.Hr(),
		dbc.Row(
			[
				dbc.Col(cardControlPanel, md=4),
				dbc.Col(dcc.Graph(id="control-panel"), md=8)
			],
			align="center",
		),
	],
	fluid=True
)

content = html.Div(id="page-content")

app.layout = html.Div([dcc.Location(id="url"), navBar, content])

@app.callback(Output("page-content", "children"), 
			[Input("url", "pathname")])
def render_page_content(pathname):
    if pathname == "/panelControl":
        return html.Div([layoutControlPanel])
    elif pathname == "/nodosAnimacion":
        return html.P("Aqui van los Nodos")

if __name__ == " __main__":
	app.run_server(debug=True)

```