On Sat, Apr 17, 2010 at 12:40 PM, Martin Hvidberg <mar...@hvidberg.net> wrote: > I have this code, it builds up a data structure of nested lists, and filling > data in them. > My problem is that it seems that one of the lists SA[1] is not a list of > unique instances but rather individual links to the same variable. > In the example below I assign 'X' to what I intended to be the first > Compounds Name. But rather the 'X' goes into all the Compounds Name. > I thought that the [:] in SAdata.extend([CP[:]]) would ensure copies rather > than links to. > What is going wrong?
someList[:] only copies 1-level deep. If you have a list of lists, none of the inner lists will be copied; you'll get a new list of references to the same lists instead. I think your code assumes [:] copies lists recursively. Also, a.extend([b[:]]) is more efficiently and idiomatically written as a.append(b[:]) Cheers, Chris -- http://blog.rebertia.com -- http://mail.python.org/mailman/listinfo/python-list
