Duncan Booth schrieb: > sturlamolden wrote: >> 1. Can python do "pass by reference"? Are datastructures represented by >> references as in Java (I don't know yet). >> > Python only does "pass by reference", although it is more normally referred > to as "pass by object reference" to distinguish it from language where the > references refer to variables rather than objects. > > What it doesn't do is let you rebind a variable in the caller's scope which > is what many people expect as a consequence of pass by reference. If you > pass an object to a function (and in Python *every* value is an object) > then when you mutate the object the changes are visible to everything else > using the same object. Of course, some objects aren't mutable so it isn't > that easy to tell that they are always passed by reference.
This is hard to understand for an outsider. If you pass an int, a float, a string or any other "atomic" object to a function you have "pass by value" semantics. If you put a compound object like a list or a dictionary or any other object that acts as an editable data container you can return modified *contents* (list elements etc.) to the caller, exactly like in Java and different from C/C++. Peter Maas, AAchen -- http://mail.python.org/mailman/listinfo/python-list
