convert random.uniform call from python2 to python3

I have some python2 code like this

self.rng.uniform(0, cutoffs[-1])

where self.rng is mtrand.RandomState, and cutoffs[-1] is map object.

when upgraded to python3, I am getting

TypeError: float() argument must be a string or a number, not 'map'

Can someone instruct how to convert this to be python3 compatible