On Tue, May 31, 2011 at 11:28 AM, Henry Olders <henry.old...@mcgill.ca> wrote: > What I would like is that the variables which are included in the function > definition's parameter list, would be always treated as local to that function
You still mis-reading docs and explanations you received from the list. Let me try again. First, there are objects and names. Calling either of them as 'variables' is leading to this mis-understanding. Name refers to some object. Object may be referenced by several names or none. Second, when you declare function `def somefunc(a, b='c')` a and b are both local to this function. Even if there are some global a and b, they are 'masked' in somefunc scope. Docs portion you cited refer to other situation, when there is no clear indicator of 'locality', like this: def somefunc(): print a In this - and only in this - case a is considered global. Third, when you do function call like somefunc(obj1, obj2) it uses call-by-sharing model. It means that it assigns exactly same object, that was referenced by obj1, to name a. So both obj1 and _local_ a reference same object. Therefore when you modify this object, you can see that obj1 and a both changed (because, in fact, obj1 and a are just PyObject*, and point to exactly same thing, which changed). However, if you re-assign local a or global obj1 to other object, other name will keep referencing old object: obj1 = [] def somefunc(a): a.append(1) # 'a' references to the list, which is referenced by obj1, and calls append method of this list, which modifies itself in place global obj1 obj1 = [] # 'a' still references to original list, which is [1] now, it have no relation to obj1 at all somefunc(obj1) -- With best regards, Daniel Kluev -- http://mail.python.org/mailman/listinfo/python-list