On Apr 15, 10:23 am, [EMAIL PROTECTED] wrote: > As a relative new comer to Python, I haven't done a heck of a lot of > hacking around with it. I had my first run in with Python's quirky (to > me at least) tendency to assign by reference rather than by value (I'm > coming from a VBA world so that's the terminology I'm using). I was > surprised that these two cases behave so differently > > test = [[1],[2]] > x = test[0] > x[0] = 5 > test>>> [[5],[2]] > > x = 1 > test > > >>>[[5],[2]] > x > >>> 1 > > Now I've done a little reading and I think I understand the problem... > My issue is, "What's the 'best practise' way of assigning just the > value of something to a new name?" > > i.e. > test = [[1,2],[3,4]] > I need to do some data manipulation with the first list in the above > list without changing <test> > obviously x = test[0] will not work as any changes i make will alter > the original... > I found that I could do this: > x = [] + test[0] > > that gets me a "pure" (i.e. unconnected to test[0] ) list but that > concerned me as a bit kludgy > > Thanks for you time and help.
I think you understand the concept, basically you want to make a copy. Ether of these are acceptable: x = test[0][:] OR x = list(test[0]) this will also work: import copy x = copy(test[0]) Matt -- http://mail.python.org/mailman/listinfo/python-list
