Chapter 3

Branches and Loops

Comparisons, if/elif/else, for loops, while loops, running totals, and off-by-one errors.

Subject
Python
Lessons
6 lessons
Practice
11 checks
Review
3 pages

What this chapter does

Once the reader can name values and inspect types, Python can choose and repeat. This chapter teaches conditions, branches, loops, and the boundary habits that keep repeated computation honest.

Lessons

Read these in order.

The chapter opening gives the main idea. Move through these lessons next; each page reuses ideas from the pages before it.

  1. 01
    Conditions and Comparisons

    Comparisons as boolean expressions used for decisions.

  2. 02
    if, elif, and else

    Ordered branch checks, indentation, and fallback cases.

  3. 03
    for Loops and Ranges

    Repeating over sequences and ranges while tracking loop variables.

  4. 04
    while Loops

    Repeating while a condition remains true and making sure the condition can change.

  5. 05
    Running Totals

    Accumulating values across loop iterations.

  6. 06
    Off-by-One Errors

    Boundary mistakes caused by start values, stop values, counts, and indexes.

  1. •
    Conclusion

    What branches and loops prepare before reusable functions.

  2. •
    Review

    A compact review of comparisons, branches, loops, running totals, and boundaries.

  3. •
    Exercises

    Chapter-level practice for branch order, ranges, totals, while loops, and boundaries.

You are ready when

  • Use comparisons as conditions.
  • Trace if, elif, and else branches in order.
  • Use for loops with lists and ranges.
  • Use while loops when repetition depends on a condition.
  • Compute a running total.
  • Recognize off-by-one boundary mistakes.

Where this leads

  • Functions
  • Collections and Iteration
  • Files, Paths, and Modules

Chapter progress