Hi, Look at the follow command in python command line, See what's interesting?:)
>>> class A: i = 0 >>> a = A() >>> b = A() >>> a.i = 1 >>> print a.i, b.i 1 0 --------------------------------------- >>> class A: arr = [] >>> a = A() >>> b = A() >>> a <__main__.A instance at 0x00C96698> >>> b <__main__.A instance at 0x00CA0760> >>> A <class __main__.A at 0x00B314B0> >>> a.arr.append("haha") >>> print a.arr , b.arr ['haha'] ['haha'] >>> a.arr = ["xixi"] >>> print a.arr , b.arr ['xixi'] ['haha'] >>> A.arr ['haha'] >>> A.arr.append("xx") >>> A.arr ['haha', 'xx'] >>> a.arr ['xixi'] >>> b.arr ['haha', 'xx'] >>> b.arr.pop() 'xx' >>> b.arr ['haha'] >>> A.arr ['haha'] ------------------------------------- >>> class X: def __init__(self): self.arr = [] >>> m = X() >>> n = X() >>> m.arr.append("haha") >>> print m.arr, n.arr ['haha'] [] -- http://mail.python.org/mailman/listinfo/python-list