piecewise numpy function with integer arguments

Question

I define the piecewise function

def Li(x):        
    return piecewise(x, [x < 0, x >= 0], [lambda t: sin(t), lambda t: cos(t)])

And when I evaluate Li(1.0)

The answer is correct

Li(1.0)=array(0.5403023058681398),

But if I write Li(1) the answer is array(0).

I don't understand this behaviour.

Answer 1

This function runs correctly.

def Li(x):        
  return  piecewise(float(x), 
                    [x < 0, x >= 0], 
                    [lambda t: sin(t), lambda t: cos(t)])