Steven Bethard wrote:
> I'm playing around with a mapping type that uses setdefault
> as suggested
> in http://www.python.org/moin/Python3_2e0Suggestions. The
> default value
> for a missing key is either a simple value, or a value
> generated from a
> function. If it's generated from the function, it should be
> generated
> new each time so that, for example, if the default is an empty list,
> d[1] and d[2] don't access the same list. This is why 'c.x is c.x'
> should be False if I'm using the function.
>
> The best option I guess is to rewrite this with a
> _getdefault() function instead of a property:
>
> But I was hoping to avoid having two separate attributes (self._value
> and self._func) when only one should have a value at any given time.
It seems to me like you were using the property as a glorified flag.
Just use a flag.
ftypes = ('BuiltinFunctionType', 'BuiltinMethodType',
'FunctionType', 'GeneratorType', 'LambdaType',
'MethodType', 'UnboundMethodType',)
class D(dict):
def __init__(self):
self._default = None
self._call_default = False
def __getitem__(self, key):
if not key in self:
if self._call_default:
self[key] = self._default()
else:
self[key] = self._default
return dict.__getitem__(self, key)
def setdefaultvalue(self, value):
self._default = value
self._call_default = isinstance(value, ftypes)
...or:
def setdefaultvalue(self, value, call_callables=True):
self._default = value
self._call_default = callable(value) and call_callables
Robert Brewer
MIS
Amor Ministries
[EMAIL PROTECTED]
--
http://mail.python.org/mailman/listinfo/python-list
