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ADM Python P.8

Combining Loops + Decisions

Using decision logic inside repeated automation cycles.

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Your lesson guide

Objective

Nest if statements inside loops Use variables to change robot behavior Trace multi-step automation logic

Materials

For the online work: a browser and your engineering notebook. Follow the activity’s materials list for any physical build, and get teacher approval before using equipment.

Plan your time

Suggested work block: 45–60 minutes. Physical builds and projects may span several classes; follow your teacher’s schedule.

Learning Targets

  • Nest if statements inside loops
  • Use variables to change robot behavior
  • Trace multi-step automation logic

How to Use This Page

  1. Read the short lesson.
  2. Attempt every Practice Check before revealing the answer.
  3. Complete Predict It and Fix It by tracing and correcting code.
  4. Complete Modify It and Program It by writing Workcell-style Python code.
  5. Use the Mastery Check before moving to the next lesson.
Learn It

Python Idea + Workcell Connection

Real automation often combines repetition and decision-making. A loop can process multiple parts while an if statement chooses a different route for each part.

When one structure is placed inside another, indentation shows which commands belong together.

Trace one loop cycle at a time. Record the variable values before deciding which branch executes.

Worked Example

Trace This Code

Read every line and predict what the program would do before opening the practice check.

for part_number in range(4):
    destination = part_number % 2

    if destination == 0:
        arm.move_to(250, 80, 120)
    else:
        arm.move_to(250, 160, 120)
Practice Check A

Check Your Understanding

  1. What values does part_number % 2 alternate between?

    Check Answer

    0 and 1

  2. Which pallet receives part numbers 0 and 2?

    Check Answer

    The first pallet at (250, 80, 120).

  3. How many total movements occur?

    Check Answer

    4 movements, one per loop cycle.

Rule: If you missed more than one question, reread Learn It and trace the example again before continuing.

1 · Predict It

Trace the Code

Which pallet is selected for each of the four parts?

Do first: Write your answer in your engineering notebook.

Reveal Self-Check

Parts 0 and 2 go to the first pallet; parts 1 and 3 go to the second pallet.

2 · Fix It

Debug the Program

Find and correct every error before opening the answer.

for part_number in range(4):
    if part_number < 2:
    arm.move_to(250, 80, 120)
    else
        arm.move_to(250, 160, 120)
Reveal Debugging Check

Indent the first movement under the if, and add a colon after else.

3 · Modify It

Change Working Code

Change the logic so the first three parts go to Pallet 1 and the fourth goes to Pallet 2.

Success Check

  • Your code is syntactically correct.
  • The change affects only the intended Workcell behavior.
  • You can explain what changed and why.

Evidence: Paste the revised code into your engineering notebook.

4 · Program It

Build It Yourself

Create a loop that processes six parts and alternates their destination between two pallet locations.

Before You Finish

  • Trace the code once by hand.
  • Check variable names, colons, parentheses, and indentation.
  • Verify that the coordinates and logic match the written scenario.
  • Add useful comments.
Interactive Practice

Python Practice Lab

Edit the code, predict the output, then click Run Code. No physical Workcell is connected.

Browser Python

P.8 Practice

Ready
Output / Errors
Predict what the code will do, then click Run Code.

Tip: Press Ctrl+Enter (Cmd+Enter on Mac) to run. The mock arm object prints simulated Workcell actions instead of controlling hardware.

Practice Check B

Explain Your Code

Without looking back at Learn It, answer these in your notebook:

  1. What Python structure or idea did you use?
  2. What Workcell behavior would this code represent?
  3. What mistake would cause the code to behave incorrectly?
What a Strong Response Includes

A strong response names the Python idea accurately, connects it to a specific Workcell action or decision, and identifies a realistic syntax or logic error from this lesson.

Mastery Gate

Ready for the Next Lesson?

  • □ I can trace a conditional inside a loop.
  • □ I can keep nested indentation organized.
  • □ I can vary Workcell behavior from cycle to cycle.

Move on only when you can check every statement. If one is still uncertain, revisit the worked example or redo Fix It before continuing.

Command Reference

VEX Workcell Python API

Use the official VEX API only as a programming reference to verify method names and parameters. The examples use the configured arm name arm. No physical Workcell is required.

Open EXP Workcell Arm API
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Build your lesson report

Checkpoint: is your evidence ready?
  • Check calculations, units, labels, and measurements against the activity requirements.
  • Record what actually happened, including unexpected results.
  • Explain what you changed and why; attach required drawings, photos, CAD, or code in your classroom assignment.

Submit the evidence specified in the activity and your classroom assignment. The report below collects your notes, calculations, observations, and reflections; attach any required drawings, photos, CAD, or code separately.

A PDF download is not a submission. Review it, then upload it and any required attachments through your classroom assignment system.