Pass by reference?

Dale Strickland-Clark dale at out-think.NOSPAMco.uk
Thu May 25 13:58:33 CEST 2000


Interesting. That makes things a bit clearer.

Thanks to all of you who took the time to explain.

--
Dale Strickland-Clark
Out-Think Ltd, UK
Business Technology Consultants

Dale Strickland-Clark <dale at out-think.NOSPAMco.uk> wrote in message
news:8gin25$sfe$1 at supernews.com...
> There isn't much else that's relevant around this statement.
>
> DBCon is an ADO connection object. This statement deletes some rows in a
> database and should return the number deleted in delcnt - the second
> argument. However, delcnt is always zero regardless of actual count
deleted.
>
>     delcnt = 0
>     print DBCon.Execute("delete from parts where path='%s' and drive='%s'"
%
> (path, drive), delcnt, 1)
>     print delcnt
>
> However, I stuck a print statement on the front to see what was returned
and
> found a list of two items, the second of which is the count I want - but
why
> isn't it returned where it should be?
>
> Also the following program proves to me that arguments are passed by value
> and not by reference:
>
> def wibble(var):
>     var = 1
>
> x = 0
> wibble(x)
> print x
>
> It prints 0 showing that the assignment in wibble is made to a copy of x
>
> So - how do I pass a variable to a function/subroutine/method by
reference?
>
> Thanks for any insight into this.
>
> --
> Dale Strickland-Clark
> Out-Think Ltd, UK
> Business Technology Consultants
>
>
>
> Shae Erisson <shapr at uab.edu> wrote in message
> news:392C683E.AF7398D4 at uab.edu...
> > Dale Strickland-Clark wrote:
> > >
> > > How do I pass a value by reference so the called routine can update
it?
> > >
> > > Here's an extract from a routine that uses ADO on NT to access a
> database.
> > > ADO will return the number of records deleted in the second parameter
> but
> > > it's not working like this.
> > >
> > >     DBCon.Execute("delete from parts where path='%s' and drive='%s'" %
> > > (drive, path), delcnt)
> >
> > That's not enough information for me to figure out what's wrong... can
> > you post five to ten lines of code and what you think they should do?
> >
> > for every case I've ever seen, pass by reference is the norm in python.
> > you can explicity make a copy of a variable if you like though.
> >
> > here's a quick demo using the 'is' operator:
> >
> > class TestClass():
> >     def update(self, val):
> >         self.strx = val
> >
> > >>> testy = TestClass()
> > >>> x = 4
> > >>> testy.update(x)
> > >>> x is testy.strx
> > 1
> >
> > The 'is' operator returns 1 (aka true) if the two references point to
> > the same thing, which means they 'is' the same thing.
> >
> >
> > I've heard that the Redneck version of Python (they read Py3K as PyKKK)
> > returns "ain't" for false.
> >
> > I-have-the-right-to-make-fun-of-my-home-state!'ly y'rs
> > --
> > sHae mAtijs eRisson (sHae at wEbwitchEs.coM) gEnius fOr hIre
> > Control - 9 out of 10 Freaks prefer it.
> >
>
>





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