1. Introduction

• Why Study This Topic?
  Built-in exceptions in Python help identify and handle runtime errors effectively. They provide a structured way to manage issues like invalid inputs, missing files, and type mismatches, making programs more robust and user-friendly.
• What Will Be Covered?
  • Definition and types of built-in exceptions
  • Common exceptions and their causes
  • Handling exceptions using try-except-finally
  • Best practices for error management

2. Detailed Content

What are Built-in Exceptions?

Built-in exceptions are predefined error classes in Python that occur during program execution due to logical or operational errors. These built-in exceptions in Python are automatically raised when an issue arises.

2.1 Common Built-in Exceptions

2.2 Handling Built-in Exceptions

Using Try-Except to Handle Exceptions

pythonCopyEdittry:
    num = int(input("Enter a number: "))
    result = 10 / num
except ZeroDivisionError:
    print("Cannot divide by zero.")
except ValueError:
    print("Invalid input. Please enter a number.")

Explanation:

• The try block runs the code that may raise an exception.
• The except block catches and handles specific errors, particularly built-in exceptions in Python.

Using Finally for Cleanup

pythonCopyEdittry:
    file = open("data.txt", "r")
finally:
    file.close()
    print("File closed.")

Explanation:

• The finally block runs regardless of whether an exception occurs.
• It ensures that necessary cleanup, like closing files, happens.

Using Else with Try-Except

pythonCopyEdittry:
    num = int(input("Enter a number: "))
    result = 10 / num
except ZeroDivisionError:
    print("Cannot divide by zero.")
else:
    print(f"Result: {result}")

Explanation:

• The else block executes only if no exception occurs in the try block.

3. Summary

• Built-in exceptions help identify and manage common runtime errors in Python.
• The try-except-finally structure ensures proper error handling.
• Using else allows executing code only when no exception occurs.

4. Learning Outcomes

After completing this topic, learners will be able to:

• Identify and understand different built-in exceptions in Python.
• Use try-except-finally to handle errors effectively.
• Apply best practices for structured exception handling.

5. Common Interview Questions

1. What is a built-in exception in Python?
   • A predefined exception that occurs during runtime due to logical or input errors.
2. How can we handle built-in exceptions in Python?
   • Using try-except blocks to catch and manage errors.
3. What is the difference between KeyError and IndexError?
   • KeyError occurs when accessing a non-existent dictionary key, whereas IndexError occurs when accessing an invalid list index.

6. Practice Exercises

1. Write a Python program to handle ZeroDivisionError and ValueError in user input.
2. Implement a try-except-finally block to handle missing files and other built-in exceptions in Python.
3. Create a function that raises an exception when an invalid dictionary key is accessed.

7. Additional Resources

• Python Built-in Exceptions Documentation
• Tutorials on Real Python and GeeksforGeeks about Built-in Exceptions in Python.