A primary reason to use wx.SpinCtrl is to restrict the user to input integers, therefore I think that the text inside it would look better if right-aligned.
Is there a way to do this in wxPython?
Actually, there is a control you can use. It's called FloatSpin, which is in the agw sub-library. If you don't already have it, download the wxPython demo and check it out!

Mike
wxPython: Right-align the numbers in a wx.SpinCtrl