Update sankey-diagram.md

Add colorful links to the Sankey diagram.

doc/python/sankey-diagram.md

@@ -71,10 +71,17 @@ import urllib, json
 url = 'https://raw.githubusercontent.com/plotly/plotly.js/master/test/image/mocks/sankey_energy.json'
 response = urllib.request.urlopen(url)
 data = json.loads(response.read())
+
+# override gray link colors with 'source' colors
+opacity = 0.4
+data['data'][0]['node']['color'] = ['rgba(255,0,255, 0.8)' if color == "magenta" else color for color in data['data'][0]['node']['color']]
+data['data'][0]['link']['color'] = [data['data'][0]['node']['color'][src] for src in data['data'][0]['link']['source']]
+data['data'][0]['link']['color'] = [color.replace("0.8", str(opacity)) for color in data['data'][0]['link']['color']]
+
 fig = go.Figure(data=[go.Sankey(
     valueformat = ".0f",
     valuesuffix = "TWh",
-    # Define nodes
+    # Define nodes
     node = dict(
       pad = 15,
       thickness = 15,
@@ -87,8 +94,9 @@ fig = go.Figure(data=[go.Sankey(
       source =  data['data'][0]['link']['source'],
       target =  data['data'][0]['link']['target'],
       value =  data['data'][0]['link']['value'],
-      label =  data['data'][0]['link']['label']
-  ))])
+      label =  data['data'][0]['link']['label'],
+      color =  data['data'][0]['link']['color']
+))])
 
 fig.update_layout(title_text="Energy forecast for 2050<br>Source: Department of Energy & Climate Change, Tom Counsell via <a href='https://bost.ocks.org/mike/sankey/'>Mike Bostock</a>",
                   font_size=10)