Project 5: A TUI File Explorer with Python & Textual

A multi-pane file explorer like ranger. It will have a directory tree, a file listing, and a preview pane that shows the contents of text files or metadata for directories.

Quick Reference

Attribute Value
Primary Language Python
Alternative Languages Go (with Bubbletea), Rust (with Ratatui)
Difficulty Level 3: Advanced
Time Estimate 2-3 weeks
Knowledge Area Modern TUI Frameworks / Filesystem
Tooling Python, Textual library
Prerequisites Strong Python skills (OOP), basic CSS knowledge is helpful.

What You Will Build

A multi-pane file explorer like ranger. It will have a directory tree, a file listing, and a preview pane that shows the contents of text files or metadata for directories.

Why It Matters

This project builds core skills that appear repeatedly in real-world systems and tooling.

Core Challenges

  • Designing a widget-based hierarchy → maps to thinking in components, like React
  • Styling the application with Textual CSS → maps to separating presentation from logic
  • Handling asynchronous file I/O → maps to using workers to prevent UI blocking
  • Binding data to widgets → maps to reactive programming concepts

Key Concepts

  • Textual App & Widgets: Textual documentation on App and built-in widgets like DirectoryTree, DataTable.
  • Layouts and CSS: Textual’s docs on grid layouts and CSS styling.
  • Workers and run_in_thread: Handling blocking I/O without freezing the app.
  • Messages and Event Handling: on_... methods for handling user input and widget events.

Real-World Outcome

# Textual App pseudo-code
from textual.app import App
from textual.widgets import DirectoryTree, Header, Footer, Static

class FileExplorer(App):
    CSS_PATH = "styles.css"

    def compose(self):
        yield Header()
        yield DirectoryTree("./")
        yield Static(id="preview") # Preview pane
        yield Footer()

    def on_directory_tree_file_selected(self, event):
        # A message handler for when a file is clicked
        preview_pane = self.query_one("#preview")
        # Use a worker to read the file asynchronously
        self.read_file_content(event.path, preview_pane)

# styles.css
# Screen {
#     layout: horizontal;
# }
# DirectoryTree {
#     width: 33%;
# }
# #preview {
#     width: 67%;
# }

Implementation Guide

  1. Reproduce the simplest happy-path scenario.
  2. Build the smallest working version of the core feature.
  3. Add input validation and error handling.
  4. Add instrumentation/logging to confirm behavior.
  5. Refactor into clean modules with tests.

Milestones

  • Milestone 1: Minimal working program that runs end-to-end.
  • Milestone 2: Correct outputs for typical inputs.
  • Milestone 3: Robust handling of edge cases.
  • Milestone 4: Clean structure and documented usage.

Validation Checklist

  • Output matches the real-world outcome example
  • Handles invalid inputs safely
  • Provides clear errors and exit codes
  • Repeatable results across runs

References

  • Main guide: LEARN_TUI_PROGRAMMING_PROJECTS.md
  • “Fluent Python” by Luciano Ramalho