dieter at 2018/10/17 UTC+8 PM 1:15:01 wrote: > jf...@ms4.hinet.net writes: > > Gregory Ewing at 2018/10/16 UTC+8 PM 2:01:01 wrote > >> jf...@ms4.hinet.net wrote: > >> > class Structure(metaclass=StructureMeta): ... > >> > > >> > class PolyHeader(Structure): ... > >> > > >> > As my understanding, the metaclass's __init__ was called when a class was > >> > created. In the above example, both the Structure and PolyHeader called > >> > it. > >> > My question is: because the PolyHeader inherited Structure, is it > >> > reasonable > >> > for PolyHeader to call this __init__ again? Will it cause any possible > >> > trouble? > >> > >> It's reasonable for both to call it, because they're distinct > >> instances of StructureMeta, each of which need to be initialised. > > > > The PolyHeader is already initialized by inheritance. Is there any way to > > bypass this __init__? > > If there were any, you should find it described in metaclass related > documentation. > > Likely, you can ensure that followup calls of "__init__" effectively > behave as "no-op"s: let the first call place a marker in the initialized > object and check in later calls whether it is already there.
Hard to find the document of type.__init__. I can only guess it does nothing, at least no thing serious, to avoid trouble the metaclass's __init__ may cause in a class hierarchy:-) -- https://mail.python.org/mailman/listinfo/python-list
