Try, Except and Error Codes
Python Programming 2 Grades 9–12 4-day lesson 29 deliverables Teach students to keep a Python program running when a user types a bad answer. Students name the error that stops each short program, such as a ValueError or a ZeroDivisionError, and catch it with try and except. They finish a try with else and finally and use raise on purpose. Then they write a seed order form and a bill splitter that return error codes instead of crashing.
● Instant download · Lifetime access · Editable & print-ready
Print + digitalPDF, PowerPoint, Word & Google
Answer keysA key for every page
Built-in assessmentExit tickets + lesson quiz
45-minute daysEvery day planned and timed
Short coding levels practice this lesson in CodeGrove, our code lab that runs in the browser. Students write the program, run it and check it, with no account and nothing to install. Use them with the lesson or as practice later.
See the levelsWhat does this lesson cover?
Many students see an error as the end of the program and do not know how to plan for it. This lesson names six common errors and shows how try and except catch them. An error code then handles a wrong range, so a form never crashes on a bad answer.
The try-its on Days 1 and 2, the lab on Day 3 and the quiz task on Day 4 run online in CodeGrove, our in-browser code lab, so students need a computer or tablet on those days. The Safe Order Form level practices catching errors with try and except, returning error codes from a check function and finishing a try with else and finally. CodeGrove is free, with no accounts, sign-ins or installs.
Safe Order Form
Students write a safe seed order form and a safe bill splitter in CodeGrove.
Everything that's included
00 Start Here
- READ FIRST: every file in the lesson and when you use it
- Teacher Guide and Pacing: the plan for each day, what to print and how to grade
- Skills map: which standards each day teaches
01 Present
- One editable PowerPoint deck for all four days, 33 slides, with speaker notes
- Slide script: the speaker notes, printed
- Bell ringers: a short warm-up for each day
02 Student Handouts
- Guided notes: one packet for all four days, in PDF and editable Word. Students fill in the blanks during the slides, with the word bank on the page
- Vocab slip: the lesson's words and what they mean, on one page
03 Labs
- Safe Order Form: students write a safe seed order form and a safe bill splitter in CodeGrove
04 Activities
- Name That Error: students name the error each short program stops with and fix one line, on paper with computers closed
- Which Block Runs?: students decide which block runs for each typed answer and write the exact output, on paper with computers closed
- Quiz task: students fix a crash in CodeGrove, working alone, and then take the lesson quiz on paper
05 Assessment
- Exit tickets: quick questions that show who needs more help
- Lesson quiz: 8 multiple-choice questions and 2 written answers about all four days, on paper
06 Answer Keys
- 6 answer key files: a key for each day (its bell ringer, notes and exit ticket) and the activity and lab keys, plus the quiz key
Digital: Google Forms™ + Google Slides™
- 5 Google Forms™ of the exit tickets and the quiz, ready to copy into your Drive
- The multiple choice grades itself, and you grade the written answers
- A Google Slides™ copy of the deck, with the same slides and speaker notes, for Google Classroom™
- Give a Form that asks students to read code only on school-managed Chromebooks in locked mode, and use the paper version on other devices
Online: CodeGrove
- In CodeGrove: the lab on Day 3 (Safe Order Form) and the quiz task on Day 4, on a computer or tablet for each student
- Try-its on Days 1 and 2: students practice the new code in CodeGrove, and nothing is turned in
- Free to use, with no accounts, sign-ins or installs
Why teachers love this lesson
Python names each errorStudents read each short program, name the error it stops with and fix one line. Then they catch that error by name.
The type and the range need different checksA try block catches the wrong type, while an error code catches the wrong range. Together they keep a form from crashing.
Print and digitalEvery page is a print-ready PDF, and the Google Forms™ and Google Slides™ let you teach the same lesson in Google Classroom™.
Real online labsStudents write and run real Python in CodeGrove, our in-browser code lab, on a computer or tablet, with no accounts or installs.
A key for every pageEvery day has its own answer key, and every written question has a sample answer and what to look for.
Every day fits a 45-minute classEach day's plan is timed activity by activity against real reading and writing speeds.
What Teachers Say
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Leave a reviewQuestions teachers ask
How do I get the files after I buy?
Instant download right after checkout: PowerPoint and Word files you can edit, print-ready PDFs, and links that copy the Google Forms™ and Google Slides™ into your Drive.
Can I buy the whole unit or course instead?
Yes. This lesson is part of the Unit 2 bundle and the complete Python Programming 2 course. Both cost less than buying the lessons one at a time.
Is this AP Computer Science?
No. It is a full-year, non-AP second course in Python for grades 9 to 12. For AP, see our AP Computer Science A and AP CSP courses.
What should students know before this lesson?
Students know how to change text to a number, write a check that returns True or False, and keep asking until the answer is good.
Do students need computers?
Yes, on the CodeGrove days. Each student needs a computer or tablet that's online, and CodeGrove needs no account or install. The bell ringers, notes, exit tickets and quiz are on paper.
What formats are the files in?
Every page is a print-ready PDF. The slides are an editable PowerPoint and the guided notes an editable Word file. The exit tickets and the quiz also come as Google Forms™, and the deck as Google Slides™.
Which standards does it cover?
Written for Florida's Intermediate Programming course (9007220). The skills map in the lesson shows which standards each day teaches.