Pass by reference or by value?

James Stroud jstroud at
Sat Jul 14 01:02:42 CEST 2007

Erik Max Francis wrote:
> James Stroud wrote:
>> Robert Dailey wrote:
>>> I noticed in Python all function parameters seem to be passed by
>>> reference. This means that when I modify the value of a variable of a
>>> function, the value of the variable externally from the function is
>>> also modified.
>>> Sometimes I wish to work with "copies", in that when I pass in an
>>> integer variable into a function, I want the function to be modifying
>>> a COPY, not the reference. Is this possible?
>> Not only is this possible, that is actually what happens with ints!
> But that's because ints are immutable, not because there is an explicit 
> copy of anything being made.

Yes. I was taking his quotes around "copies" to mean a description of 
behavior and not implementation.


James Stroud
UCLA-DOE Institute for Genomics and Proteomics
Box 951570
Los Angeles, CA 90095

More information about the Python-list mailing list