Tim Harig wrote: > On 2009-06-11, Duncan Booth <duncan.bo...@invalid.invalid> wrote: >> Tim Harig <user...@ilthio.net> wrote: >>>> number 3 never gets printed. Does Python make a copy of a list before >>>> it iterates through it?: >>> No, complex types are passed by reference unless explicity copied. >> *All* types are passed by reference unless explicitly copied. Python does >> make special cases for simple and complex types. > > That is technically true; but, you will not have this issue with simple > singlular data types. Technically the difference as to whether you will > have this problem depends on whether or not an object is mutable. > Simple objects (numbers and strings) are all immutable. Since this issue > revolves around changing objects in place, it cannot arise with immutable > objects. I am not always conscous of whether I am working with objects > that are mutable or immutable; but, I am generally concious of the general > complexity of the object. Whenever I am working with objects that are > complex, I am reminded to watch out for mutability issues. So, while it is > not > totally correct to think of it this way, I find it an easier guideline to > follow.
Everything is passed as an object[1], no matter how simple or complex, mutable or immutable. This can be seen: >>> def foo(a): ... print id(a) ... >>> b = 10 >>> id(b) 8578336 >>> foo(b) 8578336 [1] internally as PyObject pointer but that's implementation detail -- http://mail.python.org/mailman/listinfo/python-list
