Oooh... that's a gotcha. Shi Mu - did you understand that? There is a crucial difference as Gregor pointed out, that I missed, and I do apologise.
On 11/11/05, Gregor Lingl <[EMAIL PROTECTED]> wrote: > Liam Clarke schrieb: > > >Hi Shi, > > > >For what you're doing, nothing at all. > > > >When you use a colon, slice syntax, it defaults to [start:end] so p = > >a[:] is the same as > >p = a[0:len(a)] > > > > > > > But in fact there is a difference. I'll show you: > > >>> a=range(5) ### creates a list-object > >>> id(a) ### which has an identity > 14716520 > >>> p=a ### creates the new name p for the same object > >>> id(p) ### let's see > 14716520 ### o.k. really the same > >>> q=a[:] ### this names a *copy* of a q > >>> id(q) ### identity? > 14714840 ### different! > >>> a is p ### check if objects named a and p are identical > True ### yes > >>> a is q ### check if objects named a and q are identical > False ### no! > >>> a == q > True ### but have the same "content", i. e. two > different list-objects with the same elements > >>> > >>> ### Beware, lists are mutable: > >>> > >>> a > [0, 1, 2, 3, 4] > >>> a[1]=1001 > >>> a > [0, 1001, 2, 3, 4] > >>> p > [0, 1001, 2, 3, 4] ### object named a *and* p is changed > >>> q ### copy q of a is not changed!° > [0, 1, 2, 3, 4] > >>> > regards > Gregor > _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
