python-debugging

# Python Debugging

Debug Python scripts with breakpoints, stepping, variable inspection, and stack navigation.

## Quick Reference

```bash
# Start debugging
python scripts/debugger.py start script.py [args...]

# Breakpoints
python scripts/debugger.py break -f script.py -l 45           # Line breakpoint
python scripts/debugger.py break -f script.py -l 45 -c "x>10" # Conditional
python scripts/debugger.py break -e ValueError               # Exception breakpoint
python scripts/debugger.py breakpoints                        # List all

# Execution
python scripts/debugger.py continue   # Run until next breakpoint
python scripts/debugger.py step       # Step into
python scripts/debugger.py next       # Step over
python scripts/debugger.py finish     # Run until return

# Inspection
python scripts/debugger.py locals     # Local variables
python scripts/debugger.py globals    # Global variables
python scripts/debugger.py eval "expression"
python scripts/debugger.py inspect variable_name

# Stack
python scripts/debugger.py stack      # View call stack
python scripts/debugger.py up         # Move up stack
python scripts/debugger.py down       # Move down stack

# Session
python scripts/debugger.py status     # Check status
python scripts/debugger.py quit       # End session
```

## Debugging Methodology

Debug systematically, not randomly. Follow these principles:

1. **Form a hypothesis first** - Before setting breakpoints, have a theory about what's wrong
2. **Reproduce consistently** - Ensure you can trigger the bug reliably
3. **Read error messages carefully** - They often point directly to the problem
4. **Binary search for bugs** - Narrow down by halving the search space
5. **Verify assumptions** - Use `eval` to check values are what you expect
6. **Change one thing at a time** - Isolate variables to identify root cause

## Decision Framework

| Situation | Approach |
|-----------|----------|
| Script crashes with exception | `break -e ExceptionType` → `continue` → i