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ChapterCHAPTER88Lists and Dictionaries 8This chapter presents the list and dictionary object types, both of which are collectionsof other objects. These two types are the main workhorses in almost all Pythonscripts. As you’ll see, both types are remarkably flexible: they can be changed inplace,can grow and shrink on demand, and may contain and be nested in any otherkind of object. By leveraging these types, you can build up and process arbitrarilyrich information structures in your scripts.ListsThe next stop on our built-in object tour is the Python list. Lists are Python’s mostflexible ordered collection object type. Unlike strings, lists can contain any sort ofobject: numbers, strings, and even other lists. Also, unlike strings, lists may bechanged in-place by assignment to offsets and slices, list method calls, deletion statements,and more—they are mutable objects.Python lists do the work of most of the collection data structures you might have toimplement manually in lower-level languages such as C. Here is a quick look at theirmain properties. Python lists are:Ordered collections of arbitrary objectsFrom a functional view, lists are just places to collect other objects so you cantreat them as groups. Lists also maintain a left-to-right positional orderingamong the items they contain (i.e., they are sequences).Accessed by offsetJust as with strings, you can fetch a component object out of a list by indexingthe list on the object’s offset. Because items in lists are ordered by their positions,you can also do tasks such as slicing and concatenation.152