On Apr 15, 6:23 pm, [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
Perhaps it is better to think that you bind the name 'x' to the object '42' when you write 'x=42'. > 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. To create a new list with the same elements as a sequence seq, you can use list(seq). 'list' is the type of lists, it is also a 'constructor' for list objects (the same goes for other common buit-in types, such as 'int', 'float', 'str', 'tuple', 'dict'). E.g. >>> foo = [1, 2, 3] >>> bar = list(foo) >>> foo[0] = 4 >>> foo [4, 2, 3] >>> foo = [1, 2, 3] >>> bar = list(foo) >>> bar[0] = 4 >>> bar [4, 2, 3] >>> foo [1, 2, 3] >>> HTH -- Arnaud -- http://mail.python.org/mailman/listinfo/python-list
