On 2/17/24 19:24, dn via Python-list wrote:
On 18/02/24 13:21, Jonathan Gossage wrote:
- perhaps someone knows a better/proper way to do this?
Suggested research: custom classes, ABCs, and meta-classes...
Cure the old "what do you want to accomplish" question. If it's to
channel access to
On 18/02/24 13:21, Jonathan Gossage wrote:
The problem is that if you are dealing with a library class, you may
have times when the superclass is 'object' while at other times, with a
different inheritance hierarchy, the superclass may need arguments. My
thought is that the object class __new__
On 18/02/24 12:48, Jonathan Gossage wrote:
The problem that I am facing is that when the superclass is not
'object', the __init__ method may well need arguments. I do not know how
to determine if the superclass is 'object'. For what it is worth, any
attempt to use this with different arguments
On 18/02/24 11:35, Jonathan Gossage via Python-list wrote:
I am attempting to use the __new__ method in the following code:
class SingletonExample(object):
_instance = None
def __new__(cls, **kwargs):
if cls._instance is None:
cls._instance = super().__new__(cls,
On 2024-02-17 22:35, Jonathan Gossage via Python-list wrote:
I am attempting to use the __new__ method in the following code:
class SingletonExample(object):
_instance = None
def __new__(cls, **kwargs):
if cls._instance is None:
cls._instance = super().__new__(cl
I am attempting to use the __new__ method in the following code:
class SingletonExample(object):
_instance = None
def __new__(cls, **kwargs):
if cls._instance is None:
cls._instance = super().__new__(cls, **kwargs)
return cls._instance
def __init__(self, *
On Feb 9, 1:38 am, Freek Dijkstra <[EMAIL PROTECTED]> wrote:
> J Peyret wrote:
[...]
> I'll use __metaclass__ solution. Here is my (non-threaded) version:
Great! There's nothing voodoo about metaclasses.
> class RDFObject(object):
> _cache = {} # class variable is shared among all RDFObject
Matt Nordhoff <[EMAIL PROTECTED]> writes:
> Steven D'Aprano wrote:
>> Except that using has_key() means making an attribute lookup, which takes
>> time.
>
> I was going to say that, but doesn't 'in' require an attribute lookup of
> some sort too, of __contains__ or whatever?
It doesn't. Frequen
On Feb 8, 5:38 pm, Freek Dijkstra <[EMAIL PROTECTED]> wrote:
If you want to subclass, my initial example did not cover that. This
will, or at least, I don't have any problems with similar code:
... def __new__(cls,uri,*args,**kwds):
... try:
... return cls.cache[(cls,uri
On Sat, 09 Feb 2008 01:20:00 +, Matt Nordhoff wrote:
> Steven D'Aprano wrote:
>> Except that using has_key() means making an attribute lookup, which
>> takes time.
>
> I was going to say that, but doesn't 'in' require an attribute lookup of
> some sort too, of __contains__ or whatever?
I d
J Peyret wrote:
> >>> class RDFObject(object):
>
> ... cache ={}
> ... isInitialized = False
> ... def __new__(cls,uri,*args,**kwds):
> ... try:
> ... return cls.cache[uri]
> ... except KeyError:
> ... print "cache miss"
> ... res = c
Steven D'Aprano wrote:
> Except that using has_key() means making an attribute lookup, which takes
> time.
I was going to say that, but doesn't 'in' require an attribute lookup of
some sort too, of __contains__ or whatever? has_key is probably now just
a wrapper around that, so it would be one mo
En Fri, 08 Feb 2008 22:04:26 -0200, Matt Nordhoff
<[EMAIL PROTECTED]> escribió:
> J Peyret wrote:
>> - Same with using try/except KeyError instead of in cls.cache.
>> Has_key might be better if you insist on look-before-you-leap, because
>> 'in cls.cache' probably expends to uri in cls.cache.key
On Sat, 09 Feb 2008 00:04:26 +, Matt Nordhoff wrote:
> At worst, in and has_key are "about the same".
Except that using has_key() means making an attribute lookup, which takes
time.
I'm kinda curious why you say they're "about the same" when your own
timing results contradict that. Here th
J Peyret wrote:
> - Same with using try/except KeyError instead of in cls.cache.
> Has_key might be better if you insist on look-before-you-leap, because
> 'in cls.cache' probably expends to uri in cls.cache.keys(), which can
> be rather bad for perfs if the cache is very big. i.e. dict lookups
>
I think the metaclass stuff is a bit too black magic for a pretty
simple requirement.
Txs in any case for showing me the __init__ issue, I wasn't aware of
it.
Here's a workaround - not exactly elegant in terms of OO, with the
isInitialized flag, but it works.
>>> class RDFObject(object):
...
On Feb 8, 4:44 pm, Freek Dijkstra <[EMAIL PROTECTED]> wrote:
> Is there a best practice on how to override __new__?
>
> I have a base class, RDFObject, which is instantiated using a unique
> identifier (a URI in this case). If an object with a given identifier
> already exists, I want to return the
2008/2/8, Freek Dijkstra <[EMAIL PROTECTED]>:
> Is there a best practice on how to override __new__?
>
> I have a base class, RDFObject, which is instantiated using a unique
> identifier (a URI in this case). If an object with a given identifier
> already exists, I want to return the existing ob
Is there a best practice on how to override __new__?
I have a base class, RDFObject, which is instantiated using a unique
identifier (a URI in this case). If an object with a given identifier
already exists, I want to return the existing object, otherwise, I
want to create a new object and add thi
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