Bruce Whealton <br...@futurewavedesigns.com> wrote: > For lists, when would > you use what appears to be nested lists, like: > [[], [], []] > a list of lists?
Well, you'd use it when you'd want a list of lists ;) There's nothing magical about a list of lists, it's just a list with objects inside like any other, in this case they just happen to be lists. Possibly the canonical example is for a simple multidimensional array: >>> array5x5 = [[0]*5 for i in range(5)] >>> array5x5[2][3] = 7 >>> array5x5[4][1] = 2 >>> array5x5 [[0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 7, 0], [0, 0, 0, 0, 0], [0, 2, 0, 0, 0]] > Would you, and could you combine a dictionary with a list in this fashion? Lists can contain dictionaries that contain dictionaries containing lists :) So yes, they can easily be combined. Here's a list with dictionaries: elements = [ {'tag': 'strong', 'style': 'bold'}, {'tag': 'header', 'style': 'bolder', 'color': 'red}, ] And a dictionary of lists: classes_2010 = { 'economics': ['John Crowley', 'Jack Savage', 'Jane Austen'], 'voodoo economics': ['Ronald Reagan', 'Ferris Beuller'], } (Note that the formatting style is a personal taste and not essential). Generally, you tend to use a list when you want to work on items in sequence, and a dictionary when you want to work on an item on demand. > Next, from the documentation I see and this is just an example (this > kind of notation is seen elsewhere in the documentation: > > str.count(sub[, start[, end]]) > This particular example is from the string methods. > Is this a nesting of two lists inside a a third list? I know that it > would suggest that some of the arguments are optional, so perhaps if > there are 2 items the first is the sub, and the second is start? Or did In documentation (as opposed to code), [] represents optional arguments, and have nothing at all to do with Python lists. The above example is showing that the method can be called in the following ways: 'foobarbazbam'.count('ba') 'foobarbazbam'.count('ba', 6) 'foobarbazbam'.count('ba', 6, 9) Hope this helps. -- http://mail.python.org/mailman/listinfo/python-list