init_callbacks_function.py

def init_callbacks(app, countFreq):
    @app.callback(
        [dash.dependencies.Output('frequency_word_bargraph', 'figure'),
        dash.dependencies.Output('matplotlib-graph', 'src')],
        [dash.dependencies.Input('range_frequency_number', 'value')])
    def update_graph(value):
        
        newGraph = countFreq[value[0]:value[1]]
        wordcloud = WordCloud(height=500, width=500, background_color="white", contour_color='white', colormap="magma").generate_from_frequencies(newGraph)
        buf = io.BytesIO() # in-memory files
        plt.figure()
        plt.imshow(wordcloud, interpolation="bilinear")
        plt.axis("off")
        plt.savefig(buf, format = "png", dpi=600, bbox_inches = 'tight', pad_inches = 0) # save to the above file object
        data = base64.b64encode(buf.getbuffer()).decode("utf8") # encode to html elements
        plt.close()
        
        return [
                    {
                    'data': [
                        {
                            'x': newGraph.index,
                            'y': newGraph.values,
                            'name': 'first example in Dash',
                            'type': 'bar'
                        }
                    ],
                    'layout': {
                        'title': 'Coronvirus Tweet Word Frequency.'
                    }
                    },
                    "data:image/png;base64,{}".format(data)
                ]