Practical Programming, 3rd Edition

Comparing Collections

You’ve now seen strings, lists, sets, tuples, and dictionaries. They all have their uses. Here is a table comparing them:

Table 17. Features of Python Collections

Collection	Mutable?	Ordered?	Use When…
str	No	Yes	You want to keep track of text.
list	Yes	Yes	You want to keep track of an ordered sequence that you want to update.
tuple	No	Yes	You want to build an ordered sequence that you know won’t change or that you want to use as a key in a dictionary or as a value in a set.
set	Yes	No	You want to keep track of values, but order doesn’t matter, and you don’t want to keep duplicates. The values must be immutable.
dictionary	Yes	No	You want to keep a mapping ...