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+# Python Programming for Economics and Finance - Lecture Series
+
+This repository contains QuantEcon's Python Programming lecture series built using Jupyter Book. The lectures are written in MyST Markdown format and compiled into HTML, PDF, and Jupyter notebook formats.
+
+Always reference these instructions first and fallback to search or bash commands only when you encounter unexpected information that does not match the info here.
+
+## Working Effectively
+
+### Environment Setup
+- **NEVER CANCEL**: Environment creation takes 3+ minutes. Set timeout to 5+ minutes.
+- Create conda environment: `conda env create -f environment.yml`
+- Activate environment: `eval "$(conda shell.bash hook)" && conda activate quantecon`
+- **CRITICAL**: Always activate the quantecon environment before running any jb commands.
+
+### Building the Site
+- **NEVER CANCEL**: HTML builds take 4+ minutes. Set timeout to 8+ minutes.
+- Build HTML: `jb build lectures --path-output ./ -n -W --keep-going`
+- **NEVER CANCEL**: LaTeX dependency installation takes 20+ minutes. Set timeout to 35+ minutes.
+- Install LaTeX dependencies: `sudo apt-get update -qq && sudo apt-get install -y texlive-latex-recommended texlive-latex-extra texlive-fonts-recommended texlive-fonts-extra texlive-xetex latexmk xindy dvipng cm-super`
+- Build PDF LaTeX: `jb build lectures --builder pdflatex --path-output ./ -n -W --keep-going` -- takes 1 minute. Set timeout to 2+ minutes.
+- Build Jupyter notebooks: `jb build lectures --path-output ./ --builder=custom --custom-builder=jupyter -n -W --keep-going` -- takes 1 minute. Set timeout to 2+ minutes.
+
+### Compilation Notes
+- HTML build always succeeds but returns exit code 1 due to warnings (jax.quantecon.org unreachable) - this is normal.
+- PDF compilation using `latexmk -pdf -silent quantecon-python-programming.tex` in `_build/latex/` produces a PDF but has reference warnings - this is normal.
+- Jupyter notebook generation works reliably and is cached for subsequent builds.
+
+### Cleaning
+- Clean all builds: `jb clean lectures --all`
+- Remove build directory: `rm -rf _build`
+
+## Validation
+- **ALWAYS run these validation steps** after making changes to ensure functionality.
+- Start local server: `python -m http.server 8000 --directory _build/html`
+- Verify site loads: Navigate to `http://localhost:8000` and confirm the table of contents displays correctly.
+- **MANUAL VALIDATION REQUIREMENT**: Always test navigation by clicking through at least 3 lecture links to verify content renders properly.
+- Check output files exist:
+  - HTML: `ls -la _build/html/*.html | head -5`
+  - Notebooks: `ls -la _build/jupyter/*.ipynb | head -5` 
+  - PDF: `ls -la _build/latex/*.pdf`
+- **Always validate image rendering** by checking a lecture with plots (e.g., matplotlib or numpy lectures).
+
+### Linting and Code Quality
+- Use pylint for Python code validation: `pylint [file]`
+- **Always check MyST syntax** by ensuring the build completes without MyST parsing errors.
+- The build process includes automatic syntax validation - failed MyST parsing will stop the build.
+
+## Repository Structure
+
+### Key Directories
+- `/lectures/` - Contains all MyST Markdown lecture files
+- `/lectures/_config.yml` - Jupyter Book configuration 
+- `/lectures/_toc.yml` - Table of contents structure
+- `/_build/html/` - Generated HTML website
+- `/_build/latex/` - Generated LaTeX/PDF files  
+- `/_build/jupyter/` - Generated Jupyter notebooks
+- `/.github/workflows/` - CI/CD pipelines
+
+### Important Files
+- `environment.yml` - Conda environment specification (Python 3.13 + Anaconda + Jupyter Book stack)
+- `README.md` - Repository documentation
+- `.gitignore` - Excludes `_build/` and other build artifacts
+
+## Common Tasks
+
+### Adding New Lectures
+1. Create new `.md` file in `/lectures/` directory using MyST format
+2. Add entry to `/lectures/_toc.yml` in appropriate section
+3. Build and validate: Follow full build and validation process above
+4. **Always test** the new lecture loads correctly in the web interface
+
+### Modifying Existing Lectures  
+1. Edit the `.md` file in `/lectures/` directory
+2. Build HTML to test changes: `jb build lectures --path-output ./ -n -W --keep-going`
+3. **Always validate** the specific lecture page loads and renders correctly
+4. Check for broken internal links or references
+
+### Updating Dependencies
+1. Modify `environment.yml` for conda packages
+2. Recreate environment: `conda env remove -n quantecon && conda env create -f environment.yml`
+3. **NEVER CANCEL**: Full environment recreation takes 3+ minutes
+4. **Always test** full build process after dependency changes
+
+## Troubleshooting
+
+### Common Issues
+- **"jax.quantecon.org unreachable"**: This warning is expected due to network restrictions. Build continues normally.
+- **PDF reference warnings**: LaTeX compilation produces warnings about undefined references but still generates a usable PDF.
+- **Exit code 1 with warnings**: HTML builds return non-zero exit codes due to warnings but produce valid output.
+- **MyST parsing errors**: Check MyST syntax in affected `.md` files. Common issues: incorrect code block syntax, malformed cross-references.
+
+### Build Failures
+- **Clean and rebuild**: `rm -rf _build && jb build lectures --path-output ./ -n -W --keep-going`
+- **Check conda environment**: Ensure quantecon environment is active before running jb commands
+- **LaTeX issues**: Verify LaTeX dependencies are installed if PDF compilation fails
+
+### Performance Notes
+- **First build**: Takes 4+ minutes due to notebook execution and image generation
+- **Subsequent builds**: Use Jupyter cache, typically complete in similar time
+- **PDF compilation**: Fast (~30 seconds) but may have reference issues
+- **Memory usage**: Large builds may require sufficient RAM for image processing
+
+## Expected Timing
+Reference these timing expectations when setting appropriate timeouts:
+
+- Environment creation: 3 minutes (set timeout: 5+ minutes)
+- LaTeX dependencies: 20+ minutes (set timeout: 35+ minutes)  
+- HTML build: 4-5 minutes (set timeout: 8+ minutes)
+- PDF LaTeX build: 30 seconds (set timeout: 2+ minutes)
+- Jupyter build: 45 seconds (set timeout: 2+ minutes)
+- PDF compilation: 30 seconds (set timeout: 2+ minutes)
+
+**NEVER CANCEL long-running operations** - they are expected to take significant time.
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diff --git a/.gitignore b/.gitignore
index a15f5193..d8655893 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,4 +10,7 @@ dask-worker-space
 lectures/sine_wave.py
 lectures/mathfoo.py
 lectures/mod.py
-lectures/test.py
\ No newline at end of file
+lectures/test.py
+lectures/foo.py
+lectures/*.txt
+lectures/*.csv
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