Let a class behave like it's a list in Python

Question

I have a class which is essentially a collection/list of things. But I want to add some extra functions to this list. What I would like, is the following:

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Answer 1

If you don't want to redefine every method of list, I suggest you the following approach:

class MyList:
  def __init__(self, list_):
    self.li = list_
  def __getattr__(self, method):
    return getattr(self.li, method)

This would make methods like append, extend and so on, work out of the box. Beware, however, that magic methods (e.g. __len__, __getitem__ etc.) are not going to work in this case, so you should at least redeclare them like this:

class MyList:
  def __init__(self, list_):
    self.li = list_
  def __getattr__(self, method):
    return getattr(self.li, method)
  def __len__(self):
    return len(self.li)
  def __getitem__(self, item):
    return self.li[item]
  def fancyPrint(self):
    # do whatever you want...

Please note, that in this case if you want to override a method of list (extend, for instance), you can just declare your own so that the call won't pass through the __getattr__ method. For instance:

class MyList:
  def __init__(self, list_):
    self.li = list_
  def __getattr__(self, method):
    return getattr(self.li, method)
  def __len__(self):
    return len(self.li)
  def __getitem__(self, item):
    return self.li[item]
  def fancyPrint(self):
    # do whatever you want...
  def extend(self, list_):
    # your own version of extend