On 2014-12-01 13:05, Larry Martell wrote:
> Is there a way to set the default_factory of defaultdict so that
> accesses to undefined keys get to set to the key?
>
> i.e. if d['xxx'] were accessed and there was no key 'xxx' then
> d['xxx'] would get set to 'xxx'
>
> I know I can define a function with lambda for the default_factory,
> but I don't see how to access the key. I tried:
>
> d = defaultdict(lambda: key)
You could subclass it:
class MyDefaultDict(defaultdict):
def __missing__(self, key):
#self[key] = key # if you actually want it in the dict
return key
You might also have to override the __contains__ method to always
return True if you want
value_not_in_dict = 42
my_default_dict = MyDefaultDict(int)
if value_not_in_dict in my_default_dict:
this_branch_would_always_happen()
else:
this_branch_should_never_happen
You'd also have weird behaviors with iterators as they'd only ever
iterate over things that were in the dict.
-tkc
--
https://mail.python.org/mailman/listinfo/python-list
