Build AI Apps with Python: File System Tools — AI That Reads and Writes Files | Episode 9

Claude can now read, write, and list files on your computer! In this episode, we build three file system tools that let AI interact with the real world — not just answer questions, but actually create and manage files. A workspace directory keeps everything safe. All file operations happen inside it. Three questions test the full workflow: create a file, list the workspace, read the file back. Claude picks the right tool every time. Student code: https://github.com/GoCelesteAI/build-ai-apps-python/tree/main/episode09 Every keystroke is shown on screen with 3-second pauses so you can follow along at your own pace. What You'll Learn: • Building read_file, write_file, and list_directory tools • The os module for file system operations • Workspace directory pattern for safe file access • os.path.join for secure path construction • os.path.exists for safety checks before reading • os.makedirs with exist_ok for directory creation • Same dispatch pattern from Episodes 7-8 • Tool schemas for file operations • Three-question workflow: write → list → read • Running Python scripts with :!python % Timestamps: 0:00 - Introduction 0:12 - AI That Can Touch Files (Preview) 0:44 - Creating file_tools.py 1:00 - Imports (new: os module) 1:58 - Workspace directory — safe file access 2:25 - Tool 1: read_file — see inside any file 4:10 - Tool 2: write_file — create and overwrite files 5:40 - Tool 3: list_directory — see what exists 7:02 - Save progress 7:15 - Dispatch dictionary — three file tools 8:15 - Tool definitions — three JSON schemas 12:15 - Save tool definitions 12:28 - The ask() function 14:12 - Tool handling and dispatch 15:55 - Sending results back to Claude 18:12 - Three questions: write, list, read 19:12 - Save and run 19:18 - Claude manages files — write, list, read! 21:38 - Code review 21:58 - Recap: 3 Key Takeaways 22:30 - End Screen