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ADM Python P.5

Routing with if / elif / else

Decision logic for pickup zones and pallet destinations.

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Your lesson guide

Objective

Write if statements Use elif for additional routes Use else as a fallback condition

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

  • Write if statements
  • Use elif for additional routes
  • Use else as a fallback condition

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

An if statement runs code only when its condition is True. elif adds another condition, and else catches everything that did not match earlier conditions.

Indentation is part of Python syntax. Commands belonging to a condition must be indented underneath it.

This structure is ideal for routing parts to different pallet locations.

Worked Example

Trace This Code

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

destination = 2

if destination == 1:
    arm.move_to(250, 80, 120)
elif destination == 2:
    arm.move_to(250, 160, 120)
else:
    print("Invalid destination")
Practice Check A

Check Your Understanding

  1. Which branch runs when destination is 2?

    Check Answer

    The elif destination == 2 branch.

  2. Can both the if and elif branches run in this example?

    Check Answer

    No. Once a matching branch is found, the remaining branches are skipped.

  3. What is the purpose of else?

    Check Answer

    It handles any destination that did not match the valid choices.

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 movement command runs when destination is 2? What happens if destination is 4?

Do first: Write your answer in your engineering notebook.

Reveal Self-Check

Destination 2 moves to (250, 160, 120). Destination 4 prints Invalid destination.

2 · Fix It

Debug the Program

Find and correct every error before opening the answer.

destination = 1

if destination == 1
arm.move_to(250, 80, 120)
else:
    arm.move_to(250, 160, 120)
Reveal Debugging Check

Add a colon after the if condition and indent the first arm.move_to beneath it.

3 · Modify It

Change Working Code

Add a third destination that sends the arm to x=250, y=240, z=120.

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

Write routing logic for three pickup zones. Each zone should assign different pickup coordinates.

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.5 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 write if/elif/else logic.
  • □ I can indent conditional code correctly.
  • □ I can route the arm based on a variable.

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.