list vs tuple

[Joshua Marshall]

Marcin 'Qrczak' Kowalczyk <qrczak at knm.org.pl> wrote:
> Fri, 30 Mar 2001 15:25:14 -0500, Michael Prager <Mike.Prager at noaa.gov> pisze:

>> To the naive user, the EFFECT is different.  If the object is
>> immutable, the statement appears to act just like it does in
>> many other languages.  (It may not really act that way, but the
>> difference is hidden.)

> Indeed. Python's behavior is perfectly consistent. The problem is that
> for immutable types there is no difference between passing by value
> and passing by reference, so a naive user might think that Python
> passes by value. They don't realize that in this case there would
> be no difference and that the same behavior could be also explained
> differently.

Python does pass by value.  It's just that the "values" are references
to begin with.  In languages which pass by reference, assigning to the
formal parameter changes the caller's state.