Urizev wrote:
> Hi everyone
>
> I have developed the singleton implementation. However I have found a
> strange behaviour when using from different files. The code is
> attached.
>
> Executing main
> New singleton:
> <__main__.Singleton instance at 0x2b98be474a70>
> New singleton:
> <myset.Singleton instance at 0x2b98be474d88>
> I do not know why, but it creates two instances of the singleton. Does
> anybody know why?
Do you see it now I snipped the irrelevant output?
The problem is the structure of your program. The myset module is imported
twice by Python, once as "myset" and once as "__main__". Therefore you get
two distinct MySet classes, and consequently two distinct MySet.__instance
class attributes.
Move the
if __name__ == "__main__": ...
statements into a separate module, e. g. main.py:
import myset
import member
if __name__ == "__main__":
print "Executing main"
set1 = myset.MySet()
set2 = myset.MySet()
mbr1 = member.Member()
mbr2 = member.Member()
mbr3 = member.Member()
Now main.py and member.py share the same instance of the myset module and
should work as expected.
Peter
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