Flask route giving 404 with floating point numbers in the URL

Question

I have the following route definition in my Flask app's server.py:

@app.route('/nearby/<float:lat>/<float:long>')
def nearby(lat, long):
    for truck in db.trucks.find({'loc': {'$near': [lat, long]}}).limit(5):
        if truck.has_key('loc'):
            del truck['loc']
    return json.dumps(trucks)

But when I go to http://localhost:5000/nearby/37.7909470419234/-122.398633589404, I get a 404.

The other routes work fine, so it's an issue with this one. What am I doing wrong here?

Answer 1

The built-in FloatConverter does not handle negative numbers. Write a custom converter to handle negatives. This converter also treats integers as floats, which also would have failed.

from werkzeug.routing import FloatConverter as BaseFloatConverter

class FloatConverter(BaseFloatConverter):
    regex = r'-?\d+(\.\d+)?'

# before routes are registered
app.url_map.converters['float'] = FloatConverter

The built-in doesn't handle integers because then /1 and /1.0 would point to the same resource. Why it doesn't handle negative values is less clear.

Answer 2

Since the built in FloatConverter can only handle positive numbers, I pass the coordinates as strings, and use Python's float() method to convert them to floats.

Answer 3

As of Werkzeug 0.15 the built-in float converter has a signed=True parameter, which you can use for this:

@app.route('/nearby/<float(signed=True):lat>/<float(signed=True):long>')