Debugging #

You’re already familiar with many debugging techinques, such as:

Print statements
Trace Tables

and in this lab we will introduce how to use a build-in IDE debugger to accomplish:

Breakpoint Debugging
Step-By-Step code execution

Syllabus Topics #

B2.1.4 Construct and use common debugging techniques.

Key Vocabulary #

Word	Definition
Syntax Error	An error with the grammar (aka syntax), of the code. These are caught before the program start running. Python examples include mismatched parentheses or quotation marks, missing colon, or invalid indentations.
Runtime Error	An error discovered during the execution of a program. If it isn’t handled correctly, it will crash the program. Pyhthon examples include FileNotFoundError, TypeError, NameError, ValueError, ZeroDivisionError, IndexError, etc.
Logic Error	The code behaves differently than the programmer intended. The computer does not have any issue running the code.
Breakpoint Debugging	Using a debugger to indicate a specific line of code or a certain condition (aka breakpoint). When the code reaches the breakpoint, it will pause running the code so you can take a look at the state of the code (e.g. variables, code flow, or check if a particular branch of code is getting run.
Step-By-Step Code execution	Using a debugger to execute the code one line at a time. This allows you to watch variable values and the flow of the code in real-time.
Step Over	Execute the next method/function as a single command without inspecting or following its component steps.
Step Into	Enter the next method/function to follow its execution line-by-line.
Step Out	When inside a method/function/subroutine, return to the earlier execution context by completing remaining lines of the current method as though it were a single command.

[0] Set up #

Starter Code #

💻 Go to your dpcs/unit01_cryptography folder.

cd ~/desktop/dpcs/unit01_cryptography/

💻 Clone your repo and go into the directory. Be sure to replace yourgithubusername with your actual username.

git clone https://github.com/isf-dp-cs/lab_debugging_yourgithubusername

cd lab_debugging_yourgithubusername

💻 Enter the Poetry Shell to start the lab.

poetry shell

👾 💬 Exiting the poetry shell
When you want to exit the shell, you can type exit or ^D

Install Python Debugger #

💻 From the left-hand menu, click on the debugging tab

💻 If you haven’t installed it already, it will prompt you to install the python debugger

[1] Error Messages #

Syntax errors are easy to fix by reading error messages.

Palindrome #

At the moment, the file palindrome.py is full of syntax errors. When it runs correctly, it should allow the user to input a word, and then report whether the word is a palindrome. For example:

~Type a word, and I'll tell you if it's a palindrome~

> racecar
Congrats, it's a palindrome!

💻 Fix the syntax errors in palindrome.py

[2] IDE Debugger #

When using an IDE debugger (such as the Python Debugger in Visual Studio Code), two basic techniques are breakpoint debugging and step-by-step execution.

Go here to remind yourself how to step through the code.
Go here to read about setting breakpoints.

Arithmetic Game #

Right now, arithmetic_game.py doesn’t work properly. No matter how many answers you guess correctly, your score is always 0.0%.

💻 Use breakpoint debugging and step-by-step execution to find and fix the errors in arithmetic_game.py.

[3] Deliverables #

⚡✨ Once you complete the lab, be sure to complete these two steps:
✏️ Go to your Syllabus Content Checklist in your Google Drive and update it accordingly.
💻 Push your work to Github
git status
git add -A
git status
git commit -m "describe your code here"
git push
git remote

[4] Extension: Calculate Average #

This task requires knowledge of Lists.

Right now, calculate_average.py doesn’t work properly. It should calculate the average of a list of numbers, but it always thinks the average is 0.0.

💻 Use breakpoint debugging and step-by-step execution to find and fix the errors in calculate_average.py.