Flask route giving 404 with floating point numbers in the URL

The built-in FloatConverter has a signed argument that can enable matching signed values.

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

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Prior to Werkzeug 0.15, the built-in converter did not handle negative numbers. Write a custom converter to handle negatives. This converter also treats integers as floats, which also would have failed. The built-in doesn't handle integers because then /1 and /1.0 would point to the same resource, but for the positions you're trying to match that probably doesn't matter.

from werkzeug.routing import FloatConverter as BaseFloatConverter

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

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

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.

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>')