python - Passing Django Database Queryset to Highcharts via JSON

Question

First time poster, long time reader. I've spend quite awhile looking for an answer to this, which makes me think its something fundamental I'm missing.

I'm trying to pull data held in a database table and pass it through for display in a Highcharts plot. I'm not getting any errors from Django or by the client when inspecting source.

Using: Django 1.7 and Python 3.4

The views.py:

#unit/views.py
from django.http import JsonResponse
from django.shortcuts import render
from unit.analysis_funcs import ChartData

def chart_data_json(request):
    data = {}
    data['chart_data'] = ChartData.get_data()
    return JsonResponse(data, safe = True)

def plot(request):    
    return render(request, 'unit/data_plot.html', {})

The get_data() function:

#unit/analysis_funcs.py
from unit.models import CheckValve

class ChartData(object):    
    def get_data():
        data = {'serial_numbers': [], 'mass': []}

        valves = CheckValve.objects.all()

        for unit in valves:
            data['serial_numbers'].append(unit.serial_number)
            data['mass'].append(unit.mass)

        return data

The template:

<!-- templates/unit/data_plot.html -->
{% extends "base.html" %}

{% block extrahead %}
    <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js"></script>
    <script src="http://code.highcharts.com/highcharts.js"></script>
{% endblock %}

{% block rootcontainer %}
    <div id="container" style="width:100%; height:400px;"></div>    
{% endblock %}

{% block overwrite %}
<!-- Overwrite the base.html jQuery load and put in head for Highcharts to work -->
{% endblock %}

{% block extrajs %}
<script>
$(document).ready(function() {

    var options = {
        chart: {
            renderTo: 'container',
            type: 'line'
        },
        series: [{}]
    };
    var ChartDataURL = "{% url 'chart_data_json' %}";
    $.getJSON('ChartDataURL', function(data) {
        options.xAxis.categories = data['chart_data']['serial_numbers'];
        options.series[0].name = 'Serial Numbers';
        options.series[0].data = data['chart_data']['mass'];
        var chart = new Highcharts.Chart(options);
    });

});
</script>
{% endblock %}

Finally the urls:

from unit import views, graphs

urlpatterns = patterns('',

   url(r'^chart_data_json/', views.chart_data_json, name = 'chart_data_json'),

   url(r'^plot/', views.plot, name = 'plot'),

)

Everything seems to run, but the Highchart plot doesn't render. I think its in how I'm moving the JSON data from the view.py to the template.html, but after so long staring at it I'm going cross-eyed.

Any help would be awesome!

Answer 1

I finally got my plotting working. I found this approach here. Thanks to Harrison for posting his method!

My new views.py based on the above approach:

def plot(request, chartID = 'chart_ID', chart_type = 'line', chart_height = 500):
    data = ChartData.check_valve_data()

    chart = {"renderTo": chartID, "type": chart_type, "height": chart_height,}  
    title = {"text": 'Check Valve Data'}
    xAxis = {"title": {"text": 'Serial Number'}, "categories": data['serial numbers']}
    yAxis = {"title": {"text": 'Data'}}
    series = [
        {"name": 'Mass (kg)', "data": data['mass']}, 
        {"name": 'Pressure Drop (psid)', "data": data['pressure drop']},
        {"name": 'Cracking Pressure (psid)', "data": data['cracking pressure']}
        ]

    return render(request, 'unit/data_plot.html', {'chartID': chartID, 'chart': chart,
                                                    'series': series, 'title': title, 
                                                    'xAxis': xAxis, 'yAxis': yAxis})

Quick function for pulling database objects and passing the data:

class ChartData(object):    
    def check_valve_data():
        data = {'serial numbers': [], 'mass': [],
                 'pressure drop': [], 'cracking pressure': [], 'reseat pressure': []}

        valves = CheckValve.objects.all()

        for unit in valves:
            data['serial numbers'].append(unit.serial_number)
            data['mass'].append(unit.mass)
            data['cracking pressure'].append(unit.cracking_pressure)
            data['pressure drop'].append(unit.pressure_drop)
            data['reseat pressure'].append(unit.reseat_pressure)

        return data   

The key to Harrison's method is a mapping script to translate the Highcharts js to Python template variables:

{% extends "base.html" %}

{% block extrahead %}
    <!-- Load in jQuery and HighCharts -->
    <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js"></script>
    <script src="http://code.highcharts.com/highcharts.js"></script>
{% endblock %}

{% block heading %}
    <h1 align="center">Analysis</h1>
{% endblock %}

{% block content %}
    <div id={{ chartID|safe }} class="chart" style="height:100px; width:100%"></div>
{% endblock %}

{% block overwrite %}
<!-- Overwrite the base.html jQuery load and put in head for Highcharts to work -->
{% endblock %}

{% block extrajs %}
<!-- Maps the Python template context variables from views.py to the Highchart js variables -->
<script>
    var chart_id = {{ chartID|safe }}
    var chart = {{ chart|safe }}
    var title = {{ title|safe }}
    var xAxis = {{ xAxis|safe }}
    var yAxis = {{ yAxis|safe }}
    var series = {{ series|safe }}
</script>

<!-- Highchart js. Variable map shown above -->
<script>
$(document).ready(function() {
    $(chart_id).highcharts({
        chart: chart,
        title: title,
        xAxis: xAxis,
        yAxis: yAxis,
        series: series
    });
});
</script>
{% endblock %}

Everything works and displays correctly now!