Python Exception Handling – Bootcamp Assignments

This repository contains exercises, lab work, and an assignment completed as part of a Python bootcamp module on exception handling. The work focuses on writing robust programs that handle errors instead of crashing.

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Topics Covered

• Exception handling using try, except, else, and finally
• Handling built-in exceptions such as:
  • ValueError
  • ZeroDivisionError
  • FileNotFoundError
• Raising and catching custom exceptions
• Using loops for input validation
• Safe file handling
• User-friendly error reporting
• UML activity diagrams for exception flow

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Exercises

1. Age Input Validation

• Prompted the user for their age
• Used a try...except ValueError block to handle non-numeric input
• Repeatedly asked for input until a valid age was entered

2. Safe Division Function

• Created a function that divides two numbers
• Used try...except ZeroDivisionError
• Returned None when division by zero occurred

3. File Number Reader

• Read numbers from a text file line by line
• Handled:
  • FileNotFoundError when the file does not exist
  • ValueError when a line could not be converted to an integer
• Skipped invalid lines without crashing

4. UML Activity Diagram

• Drew a UML-style activity diagram to visualise:
  • Normal execution flow (no exception)
  • Exception raised and caught
  • Guaranteed execution of the finally block

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Lab Work

Individual Lab – Contact Book with Custom Exceptions

• Extended a contact book application
• Raised a custom KeyError when attempting to add a duplicate contact
• Caught the exception in the main loop and displayed a user-friendly message

Team Lab – Web Scraper with Error Handling

• Built a simple web scraper using the requests library
• Prompted the user to enter a URL, automatically prepending https:// when missing
• Implemented a while True loop to allow multiple attempts without restarting the program
• Added comprehensive exception handling to manage:
  • Invalid or malformed URLs
  • Network and connection errors
  • Request timeouts
  • HTTP status errors (e.g. 404, 500)
  • SSL-related errors
• Ensured the program displays clear, user-friendly error messages rather than crashing the program
• Demonstrated correct ordering of exception handling to avoid overly broad catches

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Assignment – Integer Input Utility

• Implemented get_int_from_user(prompt) function
• Used a while loop and try...except ValueError for validation
• Re-prompted the user until a valid integer was entered
• Returned the valid integer

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Short Answer Test

• Explained why bare except: blocks should be avoided
• Described execution flow of try...except...finally when exceptions are uncaught
• Provided a real-world scenario where else improves readability

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Tools and Technologies

• Python
• Virtual Environments (venv)
• VS Code
• Pylint
• autopep8
• Git & GitHub

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Notes

• Exception handling follows best practices by catching specific errors
• Resources are safely managed using with statements where applicable
• The virtual environment is excluded using .gitignore

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This project demonstrates safe and structured error handling techniques commonly used in professional Python development.