Hi all!
I was reading through Python Cookbook the Singleton recipe. At this moment
I am a bit puzzled as the example in the book is not working resulting in:
TypeError: type.__new__(Si ngleSpam): SingleSpam is not a subtype of type
(I haven't presented the original code as I am not sure about copyrights).
bests,
../alex
--
..w( the_mindstorm )p.
9  2008 
Alex Popescu schrieb:
Hi all!
I was reading through Python Cookbook the Singleton recipe. At this moment
I am a bit puzzled as the example in the book is not working resulting in:
TypeError: type.__new__(Si ngleSpam): SingleSpam is not a subtype of type
(I haven't presented the original code as I am not sure about copyrights).
AFAIK the cookbook is completely found online at ASPN. So no sweat
publishing it here.
And regarding the problem: is it possible that you forgot to subclass
SingleSpam from object?
Diez
"Diez B. Roggisch" <de***@nospam.w eb.dewrote in
news:5g******** *****@mid.uni-berlin.de:
Alex Popescu schrieb:
>Hi all!
I was reading through Python Cookbook the Singleton recipe. At this
moment I am a bit puzzled as the example in the book is not working
resulting in:
TypeError: type.__new__(Si ngleSpam): SingleSpam is not a subtype of
type
(I haven't presented the original code as I am not sure about
copyrights).
AFAIK the cookbook is completely found online at ASPN. So no sweat
publishing it here.
And regarding the problem: is it possible that you forgot to subclass
SingleSpam from object?
Diez
The exact code:
class Singleton(objec t):
""" A Pythonic Singleton """
def _ _new_ _(cls, *args, **kwargs):
if '_inst' not in vars(cls):
cls._inst = type._ _new_ _(cls, *args, **kwargs)
return cls._inst
if _ _name_ _ == '_ _main_ _':
class SingleSpam(Sing leton):
def _ _init_ _(self, s): self.s = s
def _ _str_ _(self): return self.s
s1 = SingleSpam('spa m')
print id(s1), s1.spam( )
s2 = SingleSpam('egg s')
print id(s2), s2.spam( )
../alex
--
..w( the_mindstorm )p.
Alex Popescu <no************ *****@gmail.com wrote in
news:Xn******** *************** ***@80.91.229.5 :
"Diez B. Roggisch" <de***@nospam.w eb.dewrote in
news:5g******** *****@mid.uni-berlin.de:
>Alex Popescu schrieb:
>>Hi all!
I was reading through Python Cookbook the Singleton recipe. At this
moment I am a bit puzzled as the example in the book is not working
resulting in:
TypeError: type.__new__(Si ngleSpam): SingleSpam is not a subtype of
type
(I haven't presented the original code as I am not sure about
copyrights) .
AFAIK the cookbook is completely found online at ASPN. So no sweat
publishing it here.
And regarding the problem: is it possible that you forgot to subclass
SingleSpam from object?
Diez
The exact code:
class Singleton(objec t):
""" A Pythonic Singleton """
def _ _new_ _(cls, *args, **kwargs):
if '_inst' not in vars(cls):
cls._inst = type._ _new_ _(cls, *args, **kwargs)
return cls._inst
if _ _name_ _ == '_ _main_ _':
class SingleSpam(Sing leton):
def _ _init_ _(self, s): self.s = s
def _ _str_ _(self): return self.s
s1 = SingleSpam('spa m')
print id(s1), s1.spam( )
s2 = SingleSpam('egg s')
print id(s2), s2.spam( )
./alex
--
.w( the_mindstorm )p.
I got it working in 2 ways:
class Singleton(objec t):
""" A Pythonic Singleton """
def __new__(cls, *args, **kwargs):
if '_singletoninst ance' not in vars(cls):
#variant 1: cls._singletoni nstance = object.__new__( cls, *args,
**kwargs)
#variant 2: cls._singletoni nstance = super(type, cls).__new__(cl s,
*args, **kwargs)
return cls._singletoni nstance
Both of these seem to work.
../alex
--
..w( the_mindstorm )p.
"Diez B. Roggisch" <de***@nospam.w eb.dewrites:
[...]
AFAIK the cookbook is completely found online at ASPN. So no sweat
publishing it here.
[...]
No: the book-form cookbook is edited, and has extra text.
I believe the recipes are under a BSD-style license, though.
John
Alex Popescu <no************ *****@gmail.com writes:
Hi all!
I was reading through Python Cookbook the Singleton recipe. At this moment
I am a bit puzzled as the example in the book is not working resulting in:
TypeError: type.__new__(Si ngleSpam): SingleSpam is not a subtype of type
Haven't looked at that recipe, but take a look at this related one: http://aspn.activestate.com/ASPN/Coo...n/Recipe/66531
John
Alex Popescu wrote:
Alex Popescu <no************ *****@gmail.com wrote in
news:Xn******** *************** ***@80.91.229.5 :
>"Diez B. Roggisch" <de***@nospam.w eb.dewrote in
news:5g******* ******@mid.uni-berlin.de:
>>Alex Popescu schrieb:
Hi all!
I was reading through Python Cookbook the Singleton recipe. At this
moment I am a bit puzzled as the example in the book is not working
resulting in:
TypeError: type.__new__(Si ngleSpam): SingleSpam is not a subtype of
type
(I haven't presented the original code as I am not sure about
copyrights ).
AFAIK the cookbook is completely found online at ASPN. So no sweat
publishing it here.
And regarding the problem: is it possible that you forgot to subclass
SingleSpam from object?
Diez
The exact code:
class Singleton(objec t):
""" A Pythonic Singleton """
def _ _new_ _(cls, *args, **kwargs):
if '_inst' not in vars(cls):
cls._inst = type._ _new_ _(cls, *args, **kwargs)
return cls._inst
if _ _name_ _ == '_ _main_ _':
class SingleSpam(Sing leton):
def _ _init_ _(self, s): self.s = s
def _ _str_ _(self): return self.s
s1 = SingleSpam('spa m')
print id(s1), s1.spam( )
s2 = SingleSpam('egg s')
print id(s2), s2.spam( )
./alex
--
.w( the_mindstorm )p.
I got it working in 2 ways:
class Singleton(objec t):
""" A Pythonic Singleton """
def __new__(cls, *args, **kwargs):
if '_singletoninst ance' not in vars(cls):
#variant 1: cls._singletoni nstance = object.__new__( cls, *args,
**kwargs)
#variant 2: cls._singletoni nstance = super(type, cls).__new__(cl s,
*args, **kwargs)
return cls._singletoni nstance
Both of these seem to work.
If, that is, "work" means "Raise an AttributeError due to the missing
spam() method". This appears to fix that problem:
class Singleton(objec t):
""" A Pythonic Singleton """
def __new__(cls, *args, **kwargs):
if '_inst' not in vars(cls):
cls._inst = object.__new__( cls, *args, **kwargs)
return cls._inst
if __name__ == '__main__':
class SingleSpam(Sing leton):
def __init__(self, s): self.s = s
def __str__(self): return self.s
s1 = SingleSpam('spa m')
print id(s1), s1
s2 = SingleSpam('egg s')
print id(s2), s2
print str(s1)
regards
Steve
--
Steve Holden +1 571 484 6266 +1 800 494 3119
Holden Web LLC/Ltd http://www.holdenweb.com
Skype: holdenweb http://del.icio.us/steve.holden
--------------- Asciimercial ------------------
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----------- Thank You for Reading -------------
Alex Popescu a écrit :
Hi all!
I was reading through Python Cookbook the Singleton recipe. At this moment
I am a bit puzzled as the example in the book is not working resulting in:
TypeError: type.__new__(Si ngleSpam): SingleSpam is not a subtype of type
(I haven't presented the original code as I am not sure about copyrights).
I don't have the book, so if you don't post the code, I just give up
trying to guess what the problem can be.
Bruno Desthuilliers <bd************ *****@free.quel quepart.frwrote in
news:46******** *************** @news.free.fr:
Alex Popescu a écrit :
>
[snip...]
I don't have the book, so if you don't post the code, I just give up
trying to guess what the problem can be.
I've sent the original code and 2 different variants a long time ago.
../alex
--
..w( the_mindstorm )p.
Alex Popescu a écrit :
Bruno Desthuilliers <bd************ *****@free.quel quepart.frwrote in
news:46******** *************** @news.free.fr:
>Alex Popescu a écrit :
>[snip...]
I don't have the book, so if you don't post the code, I just give up
trying to guess what the problem can be.
I've sent the original code and 2 different variants a long time ago.
You had not sent anything when I answered. But it seems that the machine
I answered with is a bit out of time !-)
./alex
--
.w( the_mindstorm )p.
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