Multi tool use

Unable To Plot Graph From PostgreSQL Query Results In Dash App

I am attempting to write a simple code to simply plot a bar graph of some fruit names in the x-axis vs corresponding sales units. The aim of this code is just to understand how to query postgres results from heroku hosted database through a dash app.

Below is the code,

from dash import dash
import dash_core_components as dcc
import dash_html_components as html
import plotly.graph_objs as go
import psycopg2
import os

DATABASE_URL = os.environ['DATABASE_URL']
conn = psycopg2.connect(DATABASE_URL, sslmode='require')
cur = conn.cursor()
cur.execute("SELECT fruits FROM pgrt_table")
fruits1=cur.fetchall()
#print(fruits1)
cur.execute("SELECT sales FROM pgrt_table")
sales1=cur.fetchall()


app = dash.Dash()

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

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

dcc.Graph(
id='example-graph',
figure=go.Figure(
data=[
go.Bar(
x=fruits1, y=sales1, name='SF'),
#{'x': [1, 2, 3], 'y': [2, 4, 5], 'type': 'bar', 'name': u'Montréal'},
],

#'layout':{
# 'title': 'Dash Data Visualization'
#}
)
)
])

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


The output is below,

Output to the above code

The corresponding output is just the axes with no bar graphs. The connection with the db is working since printing fruits1 or sales1 gives me the values from the columns in postgres. The only issue is the plotting.

NOTE: This question has been heavily modified since the previous draft was extremely vague without any code to show for.

'

print(fruits1)

1 Answer
1

Example:

fruits1 = [('apple',), ('banana',),
('mango',), ('pineapple',),
('peach',), ('watermelon',)]


The output of your database cannot be used directly:

xData = [fruit[0] for fruit in fruits1]
# gives ['apple', 'banana', 'mango', 'pineapple', 'peach', 'watermelon']
yData = [sales[0] for sales in sales1]


You have to assign your data to the go.Bar object:

go.Bar

go.Bar(x=xData, y=yData, name='SF')


fruits1

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.