er wrote:
Somebody much more intelligent than I said today that someone told him that Python lists are just dictionaries with lists hashed by integers.
Abstractly, which is to say, behaviorally, a Python list is a sequence class as defined under Built-in Types in the Library manual. Dictionaries are a mapping class. The two categories have different methods. So at this level, the claim is nonsensical, wrong by definition. A list *must* have it n entries indexed from 0 to n-1 and dicts do not and could not enforce such an invariant.
Concretely, an implementation could do as claimed under the covers, but CPython and I suspect all the other implementations actually use extensible arrays. People *do* use dicts for sparse arrays, but then they are *not* sequences.
Good for you for asking here. Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
