Greg Ewing 在 2021年6月15日 星期二下午3:01:46 [UTC+8] 的信中寫道： > On 15/06/21 3:18 pm, Jach Feng wrote: > > From a user's point, I don't really care how Python creates thoseinstances, > > > either using an already exist one or create a new one, as > > long as each element (and its sub-element) are independent from each > > other so a modification of one will not influence the other. The real > > problem is there are different methods can be used to build it and some > > will fail in this purpose. The * operator is one of them, but anyone > > else? I really like to know:-) > This really has nothing to do with how the tuples are created. > It all depends on what you choose to put in them. > > When you use square brackets to build a list, you can be sure that > it will create a new list object each time. > > Also, if you create two tuples, by any means, containing distinct > elements, you can be sure that you will get two distinct tuple > objects. > > So, if you do this: > > a = [1, 2] > b = [1, 2] > c = [1, 2] > d = [1, 2] > > s = (a, b) > t = (c, d) > > then you are guaranteed to get four different list objects and > two diffferent tuple objects. > > Does that help to ease your fears? > > -- > Greg But usually the list creation is not in simple way:-) for example: >>> a = [1,2] >>> m = [a for i in range(3)] >>> m [[1, 2], [1, 2], [1, 2]] >>> id(m[0]) == id(m[1]) == id(m[2]) True
--Jach -- https://mail.python.org/mailman/listinfo/python-list
