As everybody else has told you, assigning bb = aa just gives bb the reference to the same object that aa has. Unless I missed something, then nobody's actually mentioned how to make this not happen... and it's actually rather easy... instead of bb = aa, do this: bb = aa[:] Looks like a splice, and indeed it is a splice, without bounds. When a splice is used like this, I believe it is known as the copy directive.
See, when you start to do an assignment to an action on a variable (eg bb = aa*4, where a is a number, for example) bb then references an entirely new object. so, the boundless splice on aa from your examples would return a fresh copy of the original object stored in aa. Hope this helped, Brett Keith Suda-Cederquist wrote: > Hi, > > I'm using iPython and I've run into an occasional problem that I don't > understand. Here is what I'm seeing: > > >>aa=range(0,10) > >>bb=aa > >>print aa > [0,1,2,3,4,5,6,7,8,9] > >>print bb > [0,1,2,3,4,5,6,7,8,9] > >> # okay, everything allright at this point > >>bb[5]=0 #change bb > >>print aa > [0,1,2,3,4,0,6,7,8,9] #aa has changed!!! > >>print bb > [0,1,2,3,4,0,6,7,8,9] > > So the problem is that when I change bb, aa also changes even though I > don't want it to. Is this supposed to happen? If it is can someone > explain to me why this is a good thing? and finally, can someone give > me some advice on how to avoid or work-around this problem. > > Thanks, > Keith > > ------------------------------------------------------------------------ > Looking for last minute shopping deals? Find them fast with Yahoo! > Search. > <http://us.rd.yahoo.com/evt=51734/*http://tools.search.yahoo.com/newsearch/category.php?category=shopping> > > > ------------------------------------------------------------------------ > > _______________________________________________ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor > _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
