What are the arguments for scipy.stats.uniform?

In the given case the call should look like that:

uniform.rvs(loc=5, scale=45)

Even though it's possible to call the distribution directly with parameters, scipy.stats has the following logic:

<dist_name>.rvs(loc=<param1>, scale=<param2>, size=(Nx, Ny))

The first argument is the lower bound, and the second argument is the range of the distribution. So the example distribution in your question is uniform between 5 and 55.

Quoting from the documentation linked in your question:

A uniform continuous random variable.

This distribution is constant between loc and loc + scale.

loc is the first argument and scale is the second argument.