in-place operations give me the heebie-jeebies.

I think this is something that is a slightly less obvious when dealing with classes. I see stuff like this in academic code all the time:

  class SomeDataObj:
    def __init__(self, data):
      self.data = data
    
    def normalize(self):
      self.data = normalize(self.data)

I'd much prefer for there to be variable `self.data_normalized` which is initialized to None or even better a getter `getNormalizedData()` that computes/caches a normalized variable.