def get_chart_data():
    return mongo_db['item'].aggregate([
        {'$sort': {'date': 1}},
        {'$group': {
            '_id': {'year': {'$year': '$date'}, 'month': {'$month': '$date'}},
            'num': {'$sum': 1}
        }},
        {'$project': {
            'date': {'$dateFromParts' : {'year': '$_id.year', 'month': '$_id.month'}},
            'num': '$num'
        }},
        {'$sort': {'date': 1}}
    ])


def get_chart():
    data = list(get_chart_data())
    layout = plotly.graph_objs.Layout(title='Items by month')
    scatter_data = [
        plotly.graph_objs.Scatter(
            x=[d['date'] for d in data], 
            y=[d['num'] for d in data]
        )
    ]
    fig = plotly.graph_objs.Figure(data=scatter_data, layout=layout)
    return plotly.offline.plot(fig, include_plotlyjs=True, output_type='div')


@route('/chart')
def chart():
    return render_template('chart.html', chart=get_chart())

{{ chart|safe }}

from plotly.offline import init_notebook_mode, iplot
init_notebook_mode(connected=True)
iplot(get_chart())