Kay Schluehr wrote:
Why do You set
d.defaultValue(0) d.defaultValue(function=list)
but not
d.defaultValue(0) d.defaultValue([])
?
I think that's because you have to instantiate a different object for each different key. Otherwise, you would instantiate just one list as a default value for *all* default values. In other words, given:
class DefDict(dict):
def __init__(self, default):
self.default = default
def __getitem__(self, item):
try:
return dict.__getitem__(self, item)
except KeyError:
return self.defaultyou'll get
In [12]: d = DefDict([])
In [13]: d[42].extend(['foo'])
In [14]: d.default Out[14]: ['foo']
In [15]: d[10].extend(['bar'])
In [16]: d.default Out[16]: ['foo', 'bar']
In [17]: d[10] Out[17]: ['foo', 'bar']
In [18]: d[10] is d.default Out[18]: True
and this isn't what you really wanted.
By the way, to really work, I think that Duncan's proposal should create new objects when you try to access them, and to me it seems a bit counterintuitive. Nevertheless, I'm +0 on it.
And why not dict(type=int), dict(type=list) instead where default values are instantiated during object creation? A consistent pythonic handling of all types should be envisioned not some ad hoc solutions that go deprecated two Python releases later.
I don't really understand you. What should 'type' return? A callable that returns a new default value? That's exactly what Duncan proposed with the "function" keyword argument.
-- Ciao, Matteo -- http://mail.python.org/mailman/listinfo/python-list
