[FIXED] Flask Routing URL with Empty Params

Issue

How can I route a URL with empty params?

JFK-LAX for $100 works: /username=Bob/flight_search/org=JFK&dst=LAX&price=100/

JFK-(anywhere) for $100 throws 404 error: /username=Bob/flight_search/org=JFK&dst=&price=100/

The dst=& without any value seems to cause the problem.

@app.route('/username=<username>/flight_search/org=<org>&dst=<dst>&price=<price>/')
def flights(username, org, dst, price):
    flights = Flights.query.filter_by(org=org, dst=dst, price=price)
    return render_template('search_results.html', data=flights)

Solution

Rather than using variable rules to pass this data through, you should consider parsing URL params. So the request URL would look more like:

example.com/flight_search/?username=foo&org=bar&dst=&price=123

The function request.args.get() will return None if no value is set. With help from this answer you could then create the dictionary filter_data without these None values, and unpack them in the filter_by function:

@app.route('/flight_search/')
def flights():
    
    incoming_data = {}

    incoming_data['username'] = request.args.get('username')
    incoming_data['org'] = request.args.get('org')
    incoming_data['dst'] = request.args.get('dst')

    # This also supports defaults:
    incoming_data['price'] = request.args.get('price', default=100)

    filter_data = {key: value for (key, value) in incoming_data.items()
               if value}

    flights = Flights.query.filter_by(**filter_data)
    
    return render_template('search_results.html', data=flights)

Answered By - v25