On 3/26/12 4:33 PM, Steven W. Orr wrote:
On 3/26/2012 9:44 AM, Robert Kern wrote:
On 3/26/12 2:33 PM, Steven W. Orr wrote:
I created a new class called CaseInsensitiveDict (by stealing from code I found
on the web, thank you very much). The new class inherits from dict. It makes it
so that if the key has a 'lower' method, it will always access the key using
lower
I'd like to change the place where I previously declared a dict
self.lookup = defaultdict(list)
so that the new code will allow this new dict to be used instead. But then I
realized I may have painted myself into a small corner:
Is there a way to use defaultdict so that I can override what *kind* of dict it
will use?
No.
I would like the value to still be a list be default, but it seems like I can't
tell defaultdict to use *my* new dict.
Do I give up on defaultdict?
Assuming that your CaseInsensitiveDict subclasses from dict or UserDict, it's
relatively easy to make a subclass of your CaseInsensitiveDict act like a
defaultdict. Just implement the __missing__(key) method appropriately (and
modify the constructor to take the callable, of course).
http://docs.python.org/library/stdtypes.html#dict
http://docs.python.org/library/collections.html#collections.defaultdict.__missing__
I'm not quite getting what you're telling me, but I'm sure you have the right
idea. Here's the beginning of my class:
class CaseInsensitiveDict(dict):
def __init__(self, init=None):
if isinstance(init, (dict, list, tuple)):
for kk, vv in init.items():
self[self.key_has_lower(kk)] = vv
It sounds like you want me to subclass defaultdict to create something like
this?
class CaseInsensitiveDictDef(defaultdict):
def __init__(self, init=None):
super(CaseInsensitiveDictDef, self).__init__(list)
self.__missing__ = list
I think I'm way off base. I'm not clear on what the calling sequence is for
defaultdict or how to get it to use my CaseInsensitiveDict instead of regular
dict.
Can you help?
You need to make a subclass of CaseInsensitiveDict, implement the
__missing__(key) method, and override the __init__() method to take the factory
function as an argument instead of data. defaultdict is just a subclass of dict
that does this.
class CaseInsensitiveDictDef(CaseInsensitiveDict):
def __init__(self, default_factory):
super(CaseInsensitiveDictDef, self).__init__()
self.default_factory = default_factory
def __missing__(self, key):
return self.default_factory()
--
Robert Kern
"I have come to believe that the whole world is an enigma, a harmless enigma
that is made terrible by our own mad attempt to interpret it as though it had
an underlying truth."
-- Umberto Eco
--
http://mail.python.org/mailman/listinfo/python-list
