Python

CH09-03: Bridging File Reading and Writing in the OASIS

Lesson Overview:

Why Combine Reading and Writing?

Welcome back, Gunters! In the OASIS, your programs need to be smart—they must read mission logs to uncover clues and write new data to track your progress, all without letting IOI crash your terminal. So far, you’ve learned to read files (like scanning Halliday’s archives) and write files (like logging artifact discoveries). Today, we’re combining these skills to make your programs even more powerful!
In this lesson, you’ll learn how to parse structured data (like leaderboard rankings), handle tricky errors, manage files by deleting or renaming them, and monitor file sizes to keep your OASIS terminal running smoothly. These skills are like upgrading your avatar with new gear—essential for tackling real-world challenges and preparing for your final mission: a full OASIS command terminal project!

Our Objective(s)

🔍 Parse and format structured data by reading files, extracting information, and writing organized output.
🛡️ Use advanced error handling to catch specific errors and validate user input for robust programs.
🗑️ Manage files by safely deleting or renaming them to reset or archive OASIS data.
📏 Monitor file size to ensure logs don’t grow too large, simulating real-world constraints.
🔄 Combine reading and writing to create programs that process and update files in one go.
🎮 Apply these skills in OASIS-themed tasks to prepare for your final project.
✂️ Understand and use split() to break strings into manageable pieces for parsing data.

We're going to stay in the theme of Ready Player One, and visit the OASIS!! Get Ready!

🧠 Why Do We Need to Combine Reading and Writing?

The Set-Up:

Imagine you’re Parzival, updating a leaderboard after finding the Copper Key. You need to read the current rankings, check for your name, and write your new score—all without erasing everyone else’s data! Combining reading and writing lets your programs:

Load and modify saved data (like game scores or mission logs).
Create reports or summaries from raw files.
Handle files safely, even when things go wrong (like IOI hacking your terminal).

🌍 Real-World Examples

Game Development: Read a player’s saved progress, update their score, and write it back.
Data Analysis: Read a CSV file, extract specific records, and write a summary report.
Logging Systems: Read a log to check past events, then append new actions with timestamps.

✂️ Understanding the split() Function

What's this new function split( )

Before we can get into file parsing and formatting, we need to look at a new function called split( )
The split() function is like a laser cutter for string
- - It chops a string into a list of smaller strings based on a separator (like a comma, space, or colon).
  - For Example:

“1,parzival,wade watts”

- - split(",") breaks it into

["1", "parzival", "wade watts"]

- - This is super useful for reading files with structured data, like splitting a log entry into username and event.

Here's An Example of split( ) in use!!

Split will separate everything into a list based on the character :

📂 Parsing and Formatting Structured Data

What’s Parsing and Formatting?

In the OASIS, files like leaderboard.txt store data in a structured format (e.g., “rank,username,real_name”).
Parsing means reading that file and breaking it into pieces (like splitting a line into rank and username).
Formatting means writing data back in a clean, organized way (like a table or key-value pairs).

This is crucial for turning raw data into useful information, like displaying a leaderboard or summarizing mission logs.

📂ACTIVITY: Parsing the IOI Mission Logs

TASK 1: Parsing a Mission Log

STEP 1: You'll need to create the following TEXT file: mission_log.txt

parzival:Found Copper Key

art3mis:Defeated IOI Guard

parzival:Completed Jade Key Race

aech:Secured Orb of Osuvox

parzival:Entered Castle Anorak

aech:Fought at Distracted Globe

Skeleton Code To Help You...

Your Task:

Read in this file
Using readlines( ), and split( ), see if you can print out the username and mission in a nice way

Bonus points if you can have your program create that file so you don't have to

BONUS TASK:

See if you can sort these by person!!

🗑️ Basic File Deletion and Renaming

🕹️ What’s File Deletion and Renaming?

In the OASIS, you’re a Gunter managing secret mission logs. Sometimes, you need to delete a log to hide your tracks from IOI or rename it to save it as a backup. File deletion erases a file forever, like wiping a compromised data crystal. File renaming changes a file’s name, like relabeling a scroll for archiving. Python’s os module gives you two tools—os.remove() and os.rename()—to do this, but you must check if the file exists first to avoid glitches!
Both os.remove() and os.rename() can fail if the file doesn’t exist or is protected.
- - Using os.path.exists(filename) first checks if the file is there, like scanning the OASIS for a file before touching it.
  - This prevents errors and keeps your program crash-proof

Why It’s Important

Your projects might involve clearing old logs or saving backups, like archiving a mission report before IOI finds it.
These skills mimic real-world file management.

What Methods Do We Have??

os.remove(filename):

What It Does: Deletes the file named filename from your computer, like vaporizing a file in the OASIS.
Once it’s gone, it’s gone for good (no recycle bin in Python!).

How It Works:

You pass the name of the file (e.g., "player_log.txt") to os.remove(), and Python tells the operating system to delete it.
You need the os module, so import it first with import os.

When to Use It:

Use os.remove() when you want to permanently delete a file, like erasing an old log to keep IOI from finding it.

Potential Errors:

FileNotFoundError: If the file doesn’t exist, Python raises this error.

PermissionError: If the file is locked (e.g., open in another program), you can’t delete it.

IsADirectoryError: If you accidentally try to delete a folder instead of a file.

os.rename(old_name, new_name)

What It Does:
- - Changes the name of a file from old_name to new_name, like renaming a mission log from “player_log.txt” to “backup_log.txt”.
  - The file’s contents stay the same; only the name changes.

How It Works:

You pass two strings to os.rename(): the current filename and the new filename.
Python updates the file’s name in the operating system. You need import os for this too.

When to Use It:

Use os.rename() to archive files or organize data, like saving a log with a new name to mark it as a backup.

Potential Errors:

FileNotFoundError:
- - If the original file (old_name) doesn’t exist.
PermissionError:
- - If the file is locked or you don’t have permission to rename it.
FileExistsError:

If a file with new_name already exists (Python won’t overwrite it automatically).

🕹️ OASIS Terminal: Mission Log Manager

🕹️ Mission Briefing

Welcome, Gunter! You’re deep in the OASIS, managing secret mission logs to track your hunt for Halliday’s Easter egg. IOI is closing in, so you need a terminal to create, view, rename, or delete logs to stay one step ahead of Sorrento. Your program will use Python’s os module to handle files like a pro, just like Parzival hiding data from the Sixers. Ready to code your way to victory? This should take 20–25 minutes—let’s dive into the OASIS!

📋 What You’ll Do

Start-Up Function:
- - Write a function create_initial_log() that checks if mission_log.txt exists using os.path.exists().
  - If it doesn’t, create it with 3 sample entries (e.g., “parzival:Found Copper Key”).
Menu Options:
- - 1: View Mission Log:
    - - Read and display mission_log.txt’s contents, parsing each line with split(":") to show username and mission.
      - BONUS:
        Allow the user to select the delimiter that separates all the data
  - 2: Rename Mission Log:
    - - Rename mission_log.txt to “backup_mission_log.txt” using os.rename(), then read the renamed file to verify.
      - User must be prompted to rename and allowed to give a new name
  - 3: Delete Mission Log:
    - - Delete mission_log.txt using os.remove() after confirming with “Are you sure? (y/n)”.
      - BONUS: Prompt the user for the name of the file to delete
        ERROR CHECK in case it doesn't exist!!!
  - 4: Exit Terminal:
    - - Exit with a message like “Disconnecting from OASIS...”.
Error Handling:
- - Catch FileNotFoundError, PermissionError, and FileExistsError with user-friendly messages.
Interactivity:
- - Use a while loop for the menu, validate user input, and provide OASIS-themed prompts.
File Format:

mission_log.txt should have entries like “username:mission” (e.g., “art3mis:Defeated IOI Guard”).

Bonus Activities (for early finishers):

Secret Log Entry:
- - Add a menu option “5: Add Secret Log” that prompts for a username and mission, then appends it to the current log with a timestamp
    - - e.g., “2025-04-17 10:15:23 | parzival:Found Jade Key”
  - Use with open(filename, "a", encoding="utf-8")
    - - datetime.now().strftime("%Y-%m-%d %H:%M:%S").
Action Tracker:
- Create an action_log.txt file that records every rename or delete action with a timestamp (e.g., “2025-04-17 10:15:23: Renamed mission_log.txt to backup_mission_log.txt”).
- Append each action using with and "a" mode

Sample Output:

Skeleton Code:

# 🕹️ OASIS MISSION TERMINAL v1.0# HINT: Import any libraries you need (e.g., os, datetime)
# Step 1: Create the initial log if it doesn't existdef create_initial_log():    # HINT: Check if 'mission_log.txt' exists    # If not, open the file and write 3 sample mission entries    pass
# Step 2: Show menu and respond to choicesdef show_menu():    # HINT: Use a while loop to display menu until user chooses to exit    # Use input() to capture user's choice    pass
# Option 1: View Mission Logdef view_mission_log():    # HINT: Open the mission log and read the lines    # Ask the user what delimiter they want to use (default = ":")    # Split each line by the delimiter and print formatted output    pass
# Option 2: Rename Mission Logdef rename_mission_log():    # HINT: Prompt for a new filename    # Use os.rename() to rename the file    # Print confirmation and read back the file    # Log the rename action with a timestamp in 'action_log.txt'    pass
# Option 3: Delete Mission Logdef delete_mission_log():    # HINT: Ask the user which file to delete and confirm with (y/n)    # Use os.remove() to delete the file    # Be sure to check if the file exists    # Log the delete action with timestamp    pass
# Option 4: Exitdef exit_terminal():    # HINT: Print a dramatic exit message    pass
# Bonus Option 5: Add Secret Log Entrydef add_secret_log_entry():    # HINT: Ask for username and mission    # Append the entry with a timestamp to mission_log.txt    pass

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