can someone explain?

Andrew Bennetts andrew-pythonlist at
Tue Feb 18 08:04:54 CET 2003

On Tue, Feb 18, 2003 at 01:19:33AM -0500, Mongryong wrote:
> On Mon, 2003-02-17 at 11:35, Pablo wrote:
> > def increase(val):
> >   val +=1
> As other's have explained, simple types like 'ints' are
> passed-by-value.  You'll need a wrapper class for pass as reference.

Actually, everything -- including ints -- is passed by reference.

The reason it seems that things like ints are passed-by-value, is because
they are immutable.  Thus, operations like "x + y" and "val += 1" return a
new int, rather than changing the existing one in place.

Strings, all the numeric types, and tuples are immutable.


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