Python REPL - Persistent Session

Keeps Python interpreter running between commands, avoiding 20+ second package reload overhead.

When to use this skill

Use the REPL when you're about to:

• Import heavy packages: torch, transformers, nnterp, vllm, diffusers
• Run multiple Python commands that share state
• Do iterative testing/debugging with ML models
• Execute multi-step workflows (load model → compile config → query)

Don't use for one-off simple Python commands.

Setup (once per project)

uv add --editable ~/projects/research-libs/claude-repl

Quick check: Is server running?

echo '{"action":"ping"}' | timeout 2 nc -U /run/user/$(id -u)/claude-repl.sock

Start server

uv run claude-repl server &

Create session with imports

cat > /run/user/$(id -u)/session.json << 'EOF'
{
  "action": "create_session",
  "session_id": "main",
  "python_path": ["./src"],
  "preload_code": "import torch\nfrom mylib import Model\nprint('Ready')"
}
EOF
cat /run/user/$(id -u)/session.json | nc -U /run/user/$(id -u)/claude-repl.sock

Execute code

For simple code:

echo '{"action":"execute","session_id":"main","code":"print(model.num_layers)"}' | nc -U /run/user/$(id -u)/claude-repl.sock

For complex code (avoids shell escaping issues):

cat > /run/user/$(id -u)/code.py << 'EOF'
# Your code here
result = model.forward(x)
print(result.shape)
EOF

uv run python -c "
import json
code = open('/run/user/$(id -u)/code.py').read()
print(json.dumps({'action': 'execute', 'session_id': 'main', 'code': code}))
" | nc -U /run/user/$(id -u)/claude-repl.sock

Export to Jupyter notebook

Convert your session history to a notebook for sharing/reproducibility:

echo '{"action":"export_notebook","session_id":"main","path":"./experiment.ipynb"}' | nc -U /run/user/$(id -u)/claude-repl.sock

Key points

• Variables persist between execute calls
• Single-threaded: long operations block other requests
• Server uses packages from the venv it runs in
• Repo: https://github.com/Butanium/claude-repl