adding a jinja2 example to the interactive HTML export

Jinja2 is a standard, safe, and powerful way to insert content into HTML in Python.  I add an example to the documentation

Author: rl-utility-man

doc/python/interactive-html-export.md

@@ -55,6 +55,29 @@ fig.write_html("path/to/file.html")
 
 By default, the resulting HTML file is a fully self-contained HTML file which can be uploaded to a web server or shared via email or other file-sharing mechanisms. The downside to this approach is that the file is very large (5Mb+) because it contains an inlined copy of the Plotly.js library required to make the figure interactive. This can be controlled via the `include_plotlyjs` argument (see below).
 
+### Inserting Plotly Output into HTML using a Jinja2 Template
+
+You can insert Plotly output and text related to your data into HTML templates using Jinja2.   First create an HTML template file containing a variable like `{{ fig }}`.  Then use the following Python to replace `{{ fig }}` in the template with HTML that will display the Plotly figure "fig":
+
+```
+import plotly.express as px
+from jinja2 import Template
+
+data_canada = px.data.gapminder().query("country == 'Canada'")
+fig = px.bar(data_canada, x='year', y='pop')
+
+output_html_path=r"/path/to/output.html"
+input_template_path = r"/path/to/template.html"
+
+plotly_jinja_data = {"fig":fig.to_html(full_html=False)}
+#consider also defining the include_plotlyjs parameter to point to an external Plotly.js as described above
+
+with open(output_html_path, "w", encoding="utf-8") as output_file:
+    with open(input_template_path) as template_file:
+        j2_template = Template(template_file.read())
+        output_file.write(j2_template.render(plotly_jinja_data))
+```
+
 
 ### HTML export in Dash