On 12/24/2010 10:24 AM, kj wrote:
I want to implement a frozen and ordered dict.
I thought I'd implement it as a subclass of collections.OrderedDict
that prohibits all modifications to the dictionary after it has
been initialized.
In particular, calling this frozen subclass's update method should,
in general, trigger an exception ("object is not mutable").
But OrderedDict's functionality *requires* that its __init__ be
run, and this __init__, in turn, does part of its initialization
by calling the update method.
Use a flag, "private" to your new class, to indicate whether
initialization is complete or not; your update method would see that
initialization is not yet complete when called by __init__, and so it
would do its business (calling the class method). At the end of the
__init__ function, set the initialized property to true. If your update
is called with the initialized property already set to true, it will
raise the exception.
--
http://mail.python.org/mailman/listinfo/python-list
