Nesting and Choosing the Right Structure

Real data is often a structure inside a structure. The most common shape is a list of dicts, like rows in a table where each row is a record:

people = [
    {"name": "Ada", "age": 36},
    {"name": "Sam", "age": 29},
]
print(people[0]["name"])   # Ada
print(people[1]["age"])    # 29

You reach in step by step: people[0] is the first dict, then ["name"] pulls its name. Loop over the records like this:

for p in people:
    print(p["name"], p["age"])

How do you choose which structure to use? A quick guide:

• list when order matters and items can repeat (a queue, a log)
• tuple when the group is fixed and should not change (a coordinate)
• dict when you look things up by a name or id (a record, a config)
• set when you only care about unique membership (tags, seen ids)

You can mix them freely: a dict whose values are lists, a list of tuples, and so on.