Lesson 3.1
Lists and Slicing
Lists are ordered and mutable. A slice takes start, stop, and step, and the stop index is excluded.
Lessons and exercises
The four built-in collections and the habit of choosing between them. Most of the awkwardness in beginner Python comes from solving a dictionary problem with parallel lists.
Lesson 3.2
Dictionaries
A dictionary maps keys to values with constant average lookup. Keys must be hashable, which excludes lists.
Lesson 3.3
Sets and Tuples
A set stores unique unordered items with fast membership testing. A tuple is an immutable sequence, which makes it hashable and usable as a dictionary key.
Lesson 3.4
Comprehensions and Iteration Patterns
A comprehension builds a collection from an iterable in one expression, and is clearer than an accumulating loop when the logic is simple.
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