Data Stream.

Fifth class. One weight is a snapshot. Health is a stream — a series of measurements over time.

A list holds several values under one name: history = [70, 72, 74, 75]. Indexes start at 0, but today we will not dig into indexes — we will walk the whole list.

The loop for value in history: means: “for each item, call it value and run the body”. Inside you usually print(value) or do other work. Without a loop you would write print four times by hand — with a loop the code grows with the data.

Mini example:

nums = [10, 20, 30]
for n in nums:
    print(n)

You can mix constants and variables: [70, 72, 74, weight] — the last item is the current weight from earlier lessons.

Common mistake: for without indentation; or history = 70 (a number instead of a list); or printing once outside the for.