cd <flask_root_dir>/<ap_dir>

example_1:
vi templates/hello.html

vi templates/hello.html
<!doctype html>
<html>
   <body>

      <h1>Hello,{{ name }}!</h1>

   </body>
</html>
vi hello.py
from flask import Flask, render_template
ap = Flask(__name__)

@ap.route('/<who>')
def hello(who):
   return render_template('hello.html', name=who)

if __name__ == '__main__':
   ap.run(host = '0.0.0.0')
python hello.py

example_2:
vi templates/allpeople.html
<!doctype html>
<html>
   <body>
  
      <table border = 1>
         {% for key, value in people.iteritems() %}
        
            <tr>
               <th> {{ key }} </th>
               <td> {{ value }} </td>
            </tr>
           
         {% endfor %}
      </table>
     
   </body>
</html>
vi allpeople.py
from flask import Flask, render_template
ap = Flask(__name__)

@ap.route('/allpeople')
def result():
   dict = {'phoebe':1,'range':2}
   return render_template('allpeople.html', people = dict)

if __name__ == '__main__':
   ap.run(host = '0.0.0.0')

python allpeople.py

===

Jinga2 delimiters:
1.{{ Expressions to print to the template output }}
2.{% Statements %}
    1.
    {% if ... %}
    ...
    {% else %}
    ...
    {% endif %}
    2.
    {% for ... %}
    ...
    (% endfor %)
3.# Statements
    # for ... :
    ...
    # endfor
4.{# Comments not included in the template output #}
    {# ...
    ...
    #}
5.## comment
    ## ignore...

http://jinja.pocoo.org/docs/2.9/templates/#synopsis