Hendrik van Rooyen <hend...@microcorp.co.za> writes: > On Friday, 25 September 2009 19:11:06 Torsten Mohr wrote: > >> I'd like to use a nested structure in memory that consists >> of dict()s and list()s, list entries can be dict()s, other list()s, >> dict entries can be list()s or other dict()s. >> >> The lists and dicts can also contain int, float, string, ... > > This sounds terribly convoluted. > What are you trying to do? > >> >> But i'd also like to have something like a "reference" to another >> entry. > > Everything and its brother in Python is an object, and things like lists and > dicts reference objects automagically. > >> I'd like to refer to another entry and not copy that entry, i need to >> know later that this is a reference to another entry, i need to find >> also access that entry then. > > Depending on how I read this, it is either trivial or impossible: > > A name is bound to an object by assignment. > An object can have many names bound to it. > A name can, at different times, refer to different objects. > An object does not know which names are bound to it, or in what sequence it > was done. > > So you can go from name to object, but not the other way around. > You can use the same name in a loop to refer to different objects, and in > each > iteration, use the name to store a reference to the current object in a list > or dict. > >> Is something like this possible in Python? > > Not too sure what you are trying to do. > >> The references only need to refer to entries in this structure. >> The lists may change at runtime (entries removed / added), so >> storing the index may not help. > > You could start off with a list of lists of lists, to any level of nesting > that you want. This will give you a structure like a tree with branches and > twigs and leaves, but I am not sure if this is what you want or need, or if a > flat structure like third normal form would suffice, or if you need a > relational database. > > - Hendrik
I'm not really sure what he wants either, but it sounds suspiciously like a linked list. In regards to the OP, though not a true linked-list, Python objects can be built with classes that describe essentially the same functionality. Just be careful about keeping references to large in-memory objects (see weakref) and try to avoid circular references in your mappings. Cheers -- http://mail.python.org/mailman/listinfo/python-list
