D3.js and MongoDB

28 Nov

I have not been shy in my love of MongoDB. The honeymoon is not over. Now I want to graph and visualize my data from MongoDB. I just started looking at D3 – I’m coming to the party a bit late – and it is perfect for this task. I have thrown together a super simple, absurd even, example using a DB I had already populated and some left over CherryPy code. Let me say that reusing code is a good idea – when I can find what I’m looking for. It allows me to throw something together quickly. These are not production samples, but just for me to see that I can get it to work. Enough already. Here is a bar chart using D3 and MongoDB.


A Bar Chart, that should be in SVG, from MongoDB data in D3.js

I have not put this on OpenShift yet, but may.  This bar chart is a simple python script using CherryPy and committing my favorite sin – passing HTML as a variable in a return. One reason to put it on OpenShift is so I can template it in Jinja.  Here is the code:

import cherrypy
from pymongo import Connection

class mongocherry(object):

def index(self):
output =[]
output.append(‘<HTML><HEAD><TITLE>D3 and MONGODB</TITLE><script type=”text/javascript” src=”http://d3js.org/d3.v2.min.js”></script><style type=”text/css”>div.bar {display: inline-block;width: 20px;height: 75px;margin-right: 2px;background-color: teal;}</style></HEAD><BODY><h1>D3 and MongoDB</h1>’)
output.append(‘<script type=”text/javascript”>var dataset=[‘)

for x in db.places.find():
output.append(‘0];’+”\n”+’d3.select(“body”).selectAll(“div”).data(dataset).enter().append(“div”).attr(“class”, “bar”).style(“height”, function(d) {var barHeight = d * 5;return barHeight + “px”;});</script></body></html>’)

while i<len(output):

return html

index.exposed = True

cherrypy.config.update({‘server.socket_host’: ‘’,
‘server.socket_port’: 8000,


The Python code prints out HTML that looks like this:

<script type="text/javascript" src="http://d3js.org/d3.v2.min.js"></script>
<style type="text/css">
div.bar {
display: inline-block;
width: 20px;
height: 75px;
margin-right: 2px;
background-color: teal;}
<h1>D3 and MongoDB</h1>
<script type="text/javascript">
var dataset=[35,35.8,38,39,30,31,31,31,33,25,33,0];
.attr("class", "bar")
.style("height", function(d) {var barHeight = d * 5;return barHeight + "px";});

Not much going on here, just a simple D3.js bar chart – not even done in SVG. The MongoDB part is in the variable dataset[..]. While writing the HTML, the python code loops through my mongodb with for x in db.places.find(): and it grabs the latitude of the data I have with x[“loc”][0] prints it out in the JavaScript variable dataset[]. I add a 0 at the end because I get a trailing comma. Sloppy, but oh well.

I return all the HTML and you get the page displayed at the top of this post. The cool part of marrying D3.js and MongoDB is JSON. I have JSON in my DB and D3 takes JSON.


6 Responses to “D3.js and MongoDB”

  1. danudey July 4, 2013 at 8:12 pm #

    For the record, you can avoid the ‘trailing comma’ issue by doing this:

    x[“loc”][0] for x in db.places.find()

    That takes each value and joins it together using commas, instead of printing each value and then a comma regardless.

    Then at the end, instead of looping through output, you can do a few things differently:

    First, you could do ‘for line in output: html += line’; secondly, you could do html += ”.join(output). Both of these will be more efficient, and are easier to read afterwards.

    • paulcrickard July 4, 2013 at 10:13 pm #

      That is good to know. I will use the join a lot!

  2. Maria September 1, 2014 at 7:43 am #

    I am not entirely sure why you chose to give a python example using a blog style that doesn’t keep indentin information.

    • paulcrickard September 1, 2014 at 2:45 pm #

      The blog formatted the code poorly. I put it out there for me to remember as much as to show others. If it didn’t help you, sorry.


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