Flask optional routes putting /None/None in URL - flask

Question

I've been trying to set up some optional parameters like below. The user should be able to browse either the top 100, the states or the cities at any point in the heirarchy.
#app.route("/guide", defaults={'state': None, 'city': None})
#app.route("/guide/<state>", defaults={'state': None})
#app.route("/guide/<state>/<city>")
def guide_route(state, city):
if state == 'top_100':
return render_template('top_100.html')
elif state:
return render_template('state.html', data={'state': state})
elif state and city:
return render_template('city.html', data={'state': state, 'city': city})
else:
return render_template('something_else.html')
However, when I go to /guide/top_100 or /guide in my web browser, it redirects me to /guide/None/None which is a 404. What's also interesting is that I've now put print statements inside every part of the guide_route() function and none of them fire. So something isn't working in the routing table at all.
How can I get these optional parameters to work?

Answer 1

There is a mistake in the way you input the default values. You have to do it in the function definition (and not in routes) :
#app.route("/guide",)
#app.route("/guide/<string:state>")
#app.route("/guide/<string:state>/<string:city>")
def guide_route(state=None, city=None):
if state == 'top_100':
return render_template('top_100.html')
elif state and city:
return render_template('city.html', data={'state': state, 'city': city})
elif state:
return render_template('state.html', data={'state': state})
else:
return render_template('something_else.html')
https://flask.palletsprojects.com/en/2.0.x/quickstart/#variable-rules.
An example with default value : https://flask.palletsprojects.com/en/2.0.x/quickstart/#rendering-templates
(I also inverted two elif conditions)