By value or by reference?
joshway_without_spam at myway.com
Mon Oct 18 18:35:51 CEST 2004
Oliver Fromme <olli at haluter.fromme.com> wrote:
> > > > > def foo(a): a = 1
> > ...
> > > > > i = 10
> > > > > foo(i)
> > > > > print i
> > With pass-by-reference, i would now be 1. However, since python is
> > pass-by-value, it remains 10.
> It remains 10 because integers are immutable, so the function
> code cannot modify the caller's variable anyway. However, if
> you pass a mutable variable, things look a little different:
It doesn't matter that integers are immutable. Rebinding formal
parameters cannot change variables in the callers scope.
>>>> def foo(a): a = 1
>>>> i = 
>>>> print i
In this case, you're dereferencing the list (I'm using pointer-
terminolgy, but I'm still talking about the behavior of the language,
not its implemenation). You're basically modifying the object passed
into the function, not rebinding a variable.
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