[narm60]

These two aren't equivalent, the first example requires the shapename keyword arg, raising a KeyError when it wasn't specified

[Peristarkawan]

That's true. The second one might be better written as:

  def __init__(self, shapename, **kwds):

Or, in Python 3:

  def __init__(self, *, shapename, **kwds):

(making shapename a required keyword-only argument)

[reinhardt]

  def __init__(self, shapename, **kwds):

is not better written; it allows shapename to be passed positionally which makes cooperative inheritance fragile.

[Peristarkawan]

The version that I was rewriting:

  def __init__(self, shapename=None, **kwds):

also allows that.