[Python-Dev] list.__init__() vs. dict.__init__() behaviour

[Stephen Thorne]

Hi,

When testing some 'real world' code using pypy, an inconsistancy with
the way __init__ works between lists and dicts.

The assumption was made when implementing __init__ for pypy that
list.__init__ and dict.__init__ would both wipe the contents of the
objects, but it seems that in cpython, this isn't precisely the case.

>>> l = [2,3]
>>> list.__init__(l)
>>> l
[]

>>> d = {2: 3}
>>> dict.__init__(d)
>>> d
{2: 3}

dict.__init__(mydict) does not wipe the keys. list.__init__(mylist)
wipes the lists contents.

https://codespeak.net/issue/pypy-dev/issue240

Is there a good reason for this behaviour? It has broken my code (a
subclass of dict that populates a key before calling the superclasses
constructer, in the twisted codebase).

-- 
Stephen Thorne

"Give me enough bandwidth and a place to sit and I will move the world."
  --Jonathan Lange