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Chapter 39: Debugging

Complete Python lesson for very beginners. Technical words are explained in simple language, and every outline topic includes a practical example, expected output, steps, and practice.

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Chapter 39 · 15 topics
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Chapter Overview

This Python tutorial chapter covers Debugging through 15 connected topics. Work through the examples in order, check the expected output, and complete the practice after each topic.

  • 39.1 Types of Bugs
  • 39.2 Reading Tracebacks
  • 39.3 Print Debugging
  • 39.4 Debuggers
  • 39.5 Breakpoints
  • Plus 10 additional Python topics in this chapter.

39.1 Types of Bugs

Types of Bugs is part of Debugging. In simple language, it means a Python idea used while learning debugging.

It is one building block of debugging and helps you write clearer, more predictable Python programs. For a very beginner, focus first on what goes in, what Python does, and what comes out; details become easier after you run a small example.

Technical words in simple language: Types of Bugs (a Python idea used while learning debugging).

Python / Practical Example

value=3
print(f"debug value={value}")

Expected Output

debug value=3

Step-by-Step Explanation

  1. Read the example from top to bottom.
  2. Identify the value, object, or operation related to this topic.
  3. Change one small input and predict the result before running it.
Practice: Re-type the example for “Types of Bugs”, change one safe input, predict the result before running it, and explain in one sentence why the result changed.

39.2 Reading Tracebacks

Reading Tracebacks is part of Debugging. In simple language, it means a Python idea used while learning debugging.

It is one building block of debugging and helps you write clearer, more predictable Python programs. For a very beginner, focus first on what goes in, what Python does, and what comes out; details become easier after you run a small example.

Technical words in simple language: Reading Tracebacks (a Python idea used while learning debugging).

Python / Practical Example

def divide(a, b):
    return a / b

print(divide(10, 2))

Expected Output

5.0

Step-by-Step Explanation

  1. Keep the example small and reproducible.
  2. Inspect values at the point where behavior differs from expectation.
  3. Use tracebacks and breakpoints to follow the actual execution path.
Practice: Re-type the example for “Reading Tracebacks”, change one safe input, predict the result before running it, and explain in one sentence why the result changed.

39.3 Print Debugging

Print Debugging is part of Debugging. In simple language, it means finding and correcting the cause of software problems.

It makes programs easier to trust, diagnose, change, and maintain as they become larger. For a very beginner, focus first on what goes in, what Python does, and what comes out; details become easier after you run a small example.

Technical words in simple language: Print Debugging (finding and correcting the cause of software problems).

Python / Practical Example

def divide(a, b):
    return a / b

print(divide(10, 2))

Expected Output

5.0

Step-by-Step Explanation

  1. Keep the example small and reproducible.
  2. Inspect values at the point where behavior differs from expectation.
  3. Use tracebacks and breakpoints to follow the actual execution path.
Practice: Re-type the example for “Print Debugging”, change one safe input, predict the result before running it, and explain in one sentence why the result changed.

39.4 Debuggers

Debuggers is part of Debugging. In simple language, it means finding and correcting the cause of software problems.

It makes programs easier to trust, diagnose, change, and maintain as they become larger. For a very beginner, focus first on what goes in, what Python does, and what comes out; details become easier after you run a small example.

Technical words in simple language: Debuggers (finding and correcting the cause of software problems).

Python / Practical Example

def divide(a, b):
    return a / b

print(divide(10, 2))

Expected Output

5.0

Step-by-Step Explanation

  1. Keep the example small and reproducible.
  2. Inspect values at the point where behavior differs from expectation.
  3. Use tracebacks and breakpoints to follow the actual execution path.
Practice: Re-type the example for “Debuggers”, change one safe input, predict the result before running it, and explain in one sentence why the result changed.

39.5 Breakpoints

Breakpoints is part of Debugging. In simple language, it means a Python idea used while learning debugging.

It is one building block of debugging and helps you write clearer, more predictable Python programs. For a very beginner, focus first on what goes in, what Python does, and what comes out; details become easier after you run a small example.

Technical words in simple language: Breakpoints (a Python idea used while learning debugging).

Python / Practical Example

def divide(a, b):
    return a / b

print(divide(10, 2))

Expected Output

5.0

Step-by-Step Explanation

  1. Keep the example small and reproducible.
  2. Inspect values at the point where behavior differs from expectation.
  3. Use tracebacks and breakpoints to follow the actual execution path.
Practice: Re-type the example for “Breakpoints”, change one safe input, predict the result before running it, and explain in one sentence why the result changed.

39.6 Step Into

Step Into is part of Debugging. In simple language, it means a Python idea used while learning debugging.

It is one building block of debugging and helps you write clearer, more predictable Python programs. For a very beginner, focus first on what goes in, what Python does, and what comes out; details become easier after you run a small example.

Technical words in simple language: Step Into (a Python idea used while learning debugging).

Python / Practical Example

value=3
print(f"debug value={value}")

Expected Output

debug value=3

Step-by-Step Explanation

  1. Read the example from top to bottom.
  2. Identify the value, object, or operation related to this topic.
  3. Change one small input and predict the result before running it.
Practice: Re-type the example for “Step Into”, change one safe input, predict the result before running it, and explain in one sentence why the result changed.

39.7 Step Over

Step Over is part of Debugging. In simple language, it means a Python idea used while learning debugging.

It is one building block of debugging and helps you write clearer, more predictable Python programs. For a very beginner, focus first on what goes in, what Python does, and what comes out; details become easier after you run a small example.

Technical words in simple language: Step Over (a Python idea used while learning debugging).

Python / Practical Example

value=3
print(f"debug value={value}")

Expected Output

debug value=3

Step-by-Step Explanation

  1. Read the example from top to bottom.
  2. Identify the value, object, or operation related to this topic.
  3. Change one small input and predict the result before running it.
Practice: Re-type the example for “Step Over”, change one safe input, predict the result before running it, and explain in one sentence why the result changed.

39.8 Variable Inspection

Variable Inspection is part of Debugging. In simple language, it means a name that refers to a value.

It is one building block of debugging and helps you write clearer, more predictable Python programs. For a very beginner, focus first on what goes in, what Python does, and what comes out; details become easier after you run a small example.

Technical words in simple language: Variable Inspection (a name that refers to a value).

Python / Practical Example

value=3
print(f"debug value={value}")

Expected Output

debug value=3

Step-by-Step Explanation

  1. Read the example from top to bottom.
  2. Identify the value, object, or operation related to this topic.
  3. Change one small input and predict the result before running it.
Practice: Re-type the example for “Variable Inspection”, change one safe input, predict the result before running it, and explain in one sentence why the result changed.

39.9 Conditional Breakpoints

Conditional Breakpoints is part of Debugging. In simple language, it means a Python idea used while learning debugging.

It is one building block of debugging and helps you write clearer, more predictable Python programs. For a very beginner, focus first on what goes in, what Python does, and what comes out; details become easier after you run a small example.

Technical words in simple language: Conditional Breakpoints (a Python idea used while learning debugging).

Python / Practical Example

score = 82
if score >= 70:
    print("pass")

Expected Output

pass

Step-by-Step Explanation

  1. Create a condition.
  2. if runs its block only when the condition is truthy.
  3. Indent the controlled statement.
Practice: Re-type the example for “Conditional Breakpoints”, change one safe input, predict the result before running it, and explain in one sentence why the result changed.

39.10 Debugging Exceptions

Debugging Exceptions is part of Debugging. In simple language, it means an object that represents a runtime problem.

It makes programs easier to trust, diagnose, change, and maintain as they become larger. For a very beginner, focus first on what goes in, what Python does, and what comes out; details become easier after you run a small example.

Technical words in simple language: Debugging Exceptions (an object that represents a runtime problem).

Python / Practical Example

try:
    number = int("not-a-number")
except ValueError as error:
    print(type(error).__name__)

Expected Output

ValueError

Step-by-Step Explanation

  1. Put risky conversion inside try.
  2. Catch the specific ValueError you expect.
  3. Handle the problem without hiding unrelated errors.
Practice: Re-type the example for “Debugging Exceptions”, change one safe input, predict the result before running it, and explain in one sentence why the result changed.

39.11 IDE Debugging

IDE Debugging is part of Debugging. In simple language, it means finding and correcting the cause of software problems.

It makes programs easier to trust, diagnose, change, and maintain as they become larger. For a very beginner, focus first on what goes in, what Python does, and what comes out; details become easier after you run a small example.

Technical words in simple language: IDE Debugging (finding and correcting the cause of software problems).

Python / Practical Example

def divide(a, b):
    return a / b

print(divide(10, 2))

Expected Output

5.0

Step-by-Step Explanation

  1. Keep the example small and reproducible.
  2. Inspect values at the point where behavior differs from expectation.
  3. Use tracebacks and breakpoints to follow the actual execution path.
Practice: Re-type the example for “IDE Debugging”, change one safe input, predict the result before running it, and explain in one sentence why the result changed.

39.12 Logging During Debugging

Logging During Debugging is part of Debugging. In simple language, it means finding and correcting the cause of software problems.

It makes programs easier to trust, diagnose, change, and maintain as they become larger. For a very beginner, focus first on what goes in, what Python does, and what comes out; details become easier after you run a small example.

Technical words in simple language: Logging During Debugging (finding and correcting the cause of software problems).

Python / Practical Example

def divide(a, b):
    return a / b

print(divide(10, 2))

Expected Output

5.0

Step-by-Step Explanation

  1. Keep the example small and reproducible.
  2. Inspect values at the point where behavior differs from expectation.
  3. Use tracebacks and breakpoints to follow the actual execution path.
Practice: Re-type the example for “Logging During Debugging”, change one safe input, predict the result before running it, and explain in one sentence why the result changed.

39.13 Reproducing Bugs

Reproducing Bugs is part of Debugging. In simple language, it means a Python idea used while learning debugging.

It is one building block of debugging and helps you write clearer, more predictable Python programs. For a very beginner, focus first on what goes in, what Python does, and what comes out; details become easier after you run a small example.

Technical words in simple language: Reproducing Bugs (a Python idea used while learning debugging).

Python / Practical Example

value=3
print(f"debug value={value}")

Expected Output

debug value=3

Step-by-Step Explanation

  1. Read the example from top to bottom.
  2. Identify the value, object, or operation related to this topic.
  3. Change one small input and predict the result before running it.
Practice: Re-type the example for “Reproducing Bugs”, change one safe input, predict the result before running it, and explain in one sentence why the result changed.

39.14 Root-Cause Analysis

Root-Cause Analysis is part of Debugging. In simple language, it means a Python idea used while learning debugging.

It is one building block of debugging and helps you write clearer, more predictable Python programs. For a very beginner, focus first on what goes in, what Python does, and what comes out; details become easier after you run a small example.

Technical words in simple language: Root-Cause Analysis (a Python idea used while learning debugging).

Python / Practical Example

value=3
print(f"debug value={value}")

Expected Output

debug value=3

Step-by-Step Explanation

  1. Read the example from top to bottom.
  2. Identify the value, object, or operation related to this topic.
  3. Change one small input and predict the result before running it.
Practice: Re-type the example for “Root-Cause Analysis”, change one safe input, predict the result before running it, and explain in one sentence why the result changed.

39.15 Debugging Workflow

Debugging Workflow is part of Debugging. In simple language, it means finding and correcting the cause of software problems.

It makes programs easier to trust, diagnose, change, and maintain as they become larger. For a very beginner, focus first on what goes in, what Python does, and what comes out; details become easier after you run a small example.

Technical words in simple language: Debugging Workflow (finding and correcting the cause of software problems).

Python / Practical Example

def divide(a, b):
    return a / b

print(divide(10, 2))

Expected Output

5.0

Step-by-Step Explanation

  1. Keep the example small and reproducible.
  2. Inspect values at the point where behavior differs from expectation.
  3. Use tracebacks and breakpoints to follow the actual execution path.
Practice: Re-type the example for “Debugging Workflow”, change one safe input, predict the result before running it, and explain in one sentence why the result changed.

Common Beginner Mistakes

  • Copying code without predicting what each line does.
  • Ignoring the first useful error message or traceback location.
  • Mixing tabs/spaces or changing indentation accidentally.
  • Using data of the wrong type for an operation.
  • Trying to learn many advanced variations before mastering one small working example.

Chapter Practice

  1. Choose three topics from this chapter and re-type their examples without copying and pasting.
  2. For each example, change one input and predict the output first.
  3. Explain five technical terms from this chapter in your own beginner-friendly words.
  4. Create one small program that combines at least two chapter topics.
  5. Keep notes about errors you made and what fixed them.

Mini Project / Challenge

Create a small Python exercise that combines at least three ideas from Debugging. Start with a tiny working version, test it, then improve it one step at a time.

  1. Choose three topics from this chapter.
  2. Write or adapt a small Python example using those topics.
  3. Predict the output before running the code.
  4. Test at least one different input.
  5. Write two sentences explaining what the program does and what you learned.

20 Questions & Answers

1. What is the main goal of Chapter 39?

The goal is to understand debugging through small explanations, examples, and practice.

2. Should I memorize every command or method?

No. Understand the pattern, practice the common form, and learn how to read documentation when you need exact details.

3. Why are the examples small?

Small examples isolate one idea at a time, which makes errors easier to understand and fix.

4. What should I do when an example gives an error?

Read the last part of the traceback, check spelling and indentation, confirm the required package or file exists, and compare the input types with what the operation expects.

5. Why should I predict output before running code?

Prediction forces you to reason about the program instead of only copying it.

6. What should I remember about Types of Bugs?

Remember its beginner meaning, the problem it helps solve, the shape of a small example, and one common situation where it is appropriate.

7. What should I remember about Reading Tracebacks?

Remember its beginner meaning, the problem it helps solve, the shape of a small example, and one common situation where it is appropriate.

8. What should I remember about Print Debugging?

Remember its beginner meaning, the problem it helps solve, the shape of a small example, and one common situation where it is appropriate.

9. What should I remember about Debuggers?

Remember its beginner meaning, the problem it helps solve, the shape of a small example, and one common situation where it is appropriate.

10. What should I remember about Breakpoints?

Remember its beginner meaning, the problem it helps solve, the shape of a small example, and one common situation where it is appropriate.

11. What should I remember about Step Into?

Remember its beginner meaning, the problem it helps solve, the shape of a small example, and one common situation where it is appropriate.

12. What should I remember about Step Over?

Remember its beginner meaning, the problem it helps solve, the shape of a small example, and one common situation where it is appropriate.

13. What should I remember about Variable Inspection?

Remember its beginner meaning, the problem it helps solve, the shape of a small example, and one common situation where it is appropriate.

14. What should I remember about Conditional Breakpoints?

Remember its beginner meaning, the problem it helps solve, the shape of a small example, and one common situation where it is appropriate.

15. What should I remember about Debugging Exceptions?

Remember its beginner meaning, the problem it helps solve, the shape of a small example, and one common situation where it is appropriate.

16. What should I remember about IDE Debugging?

Remember its beginner meaning, the problem it helps solve, the shape of a small example, and one common situation where it is appropriate.

17. What should I remember about Logging During Debugging?

Remember its beginner meaning, the problem it helps solve, the shape of a small example, and one common situation where it is appropriate.

18. What should I remember about Reproducing Bugs?

Remember its beginner meaning, the problem it helps solve, the shape of a small example, and one common situation where it is appropriate.

19. What should I remember about Root-Cause Analysis?

Remember its beginner meaning, the problem it helps solve, the shape of a small example, and one common situation where it is appropriate.

20. What should I remember about Debugging Workflow?

Remember its beginner meaning, the problem it helps solve, the shape of a small example, and one common situation where it is appropriate.