from flask import Flask
app = Flask(__name__)

@app.route("/")
def hello():
    return "Hello World!"

@app.route("/pi")
def pi():
    return "3.1416"

if __name__ == "__main__":
    app.run()

Options +ExecCGI
AddHandler cgi-script .cgi .py .rb
DirectoryIndex index.cgi index.htm

#!/usr/bin/env python
from wsgiref.handlers import CGIHandler
from firstflask import app

CGIHandler().run(app)

Options +ExecCGI
AddHandler cgi-script .cgi .py .rb
DirectoryIndex index.cgi index.htm

RewriteEngine On
RewriteRule ^index.cgi/(.*)$ - [S=1]
RewriteRule ^(.*)$ index.cgi/$1 [QSA,L]

RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*)$ /path/to/the/application.cgi/$1 [L]