Function to create an interpolate function.

interpolation.py

def make_interpolation(from_range, to_range):
    from_min, from_max = from_range
    to_min, to_max = to_range
    scale = float(to_max - to_min) / float(from_max - from_min)
    def interpolate(value):
        return to_min + (value - from_min) * scale
    return interpolate
    
change = make_interpolation((0, 100), (0, 200))
print(change(50))  # will print 100.0