Modifying Class Object

T misceverything at gmail.com
Mon Feb 8 18:05:05 CET 2010


On Feb 8, 4:00 am, Duncan Booth <duncan.bo... at invalid.invalid> wrote:
> T <misceveryth... at gmail.com> wrote:
> > Oops, this one was my fault - the object I was having the issues with
> > was actually a shelve file, not a dictionary..so just re-assigning the
> > variable isn't working, but re-writing the object to the shelve file
> > does.  So in this case, is there any way to just change a single
> > value, or am I stuck rewriting the entry?
>
> Either open the shelve with writeback=True or rewrite the entry.
> Rewriting the entry isn't hard: you can just re-use the same value:
>
> def changevalue():
>     for key in mytest.keys():
>         temp = mytest[key]
>         temp.param3 = "newvalue"
>         mytest[key] = temp
>
> If you really are changing every item in the shelve using writeback=True
> will be much simpler, but if you are only changing a few then just tell the
> shelve that you've updated them as above.
>
> --
> Duncan Boothhttp://kupuguy.blogspot.com


Duncan - Thanks for your help.  So each of the shelve entries I'm
modifying look something like this:  myshelve[key] =
TestClassObject(param1, param2, param3, param4, param5, etc.).  In
this case, with quite a few parameters, would you suggest setting
writeback=True and just modifying the needed value, or rewriting the
entire entry?  I have to admit the writeback option looks good, and if
the TestClassObject format ever changes (i.e. if I ever change the
order of the params), this particular function will be unchanged.
However, I don't know what the performance hit would be in using it.



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