python-shell-fallback

Python Shell Fallback

When execute_code_sandbox fails for Python code that depends on external libraries, use run_shell with a heredoc Python script as a reliable fallback. The shell environment typically has better access to installed packages and system configuration than the sandbox.

When to Use This Pattern

Apply this skill when:

• execute_code_sandbox returns errors related to missing libraries (e.g., ModuleNotFoundError)
• The code requires packages that may not be installed in the sandbox environment
• You need PDF generation, data visualization, or other library-heavy operations
• Previous sandbox execution attempts have failed with import errors

How to Implement

Step 1: Identify the Failure

Check if the sandbox error indicates a library/dependency issue:

• ModuleNotFoundError: No module named 'xxx'
• ImportError: cannot import name 'xxx'
• Similar package-related errors

Step 2: Convert to Shell Execution

Rewrite the code execution using run_shell with a heredoc:

python3 << 'EOF'
# Your Python code here
import library_name
# ... rest of code
EOF

Step 3: Execute via run_shell

Call run_shell with the heredoc Python script:

command: python3 << 'EOF'
import reportlab
from reportlab.lib.pagesizes import letter
from reportlab.pdfgen import canvas

# Your library-dependent code here
c = canvas.Canvas("output.pdf", pagesize=letter)
c.drawString(100, 750, "Hello World")
c.save()
EOF

Example: PDF Generation Fallback

Sandbox attempt (fails):

# execute_code_sandbox call fails with:
# ModuleNotFoundError: No module named 'reportlab'

Shell fallback (works):

python3 << 'EOF'
from reportlab.lib.pagesizes import letter
from reportlab.pdfgen import canvas

c = canvas.Canvas("legal_memo.pdf", pagesize=letter)
c.setTitle("Legal Memorandum")
c.drawString(100, 750, "CONFIDENTIAL LEGAL MEMORANDUM")
c.save()
print("PDF created successfully")
EOF

Best Practices

1. Use quoted heredoc (<< 'EOF') - Prevents variable expansion, keeping Python code intact
2. Verify output - Check stdout/stderr from run_shell to confirm success
3. Handle file paths - Ensure output files are written to accessible directories
4. Test incrementally - For complex scripts, test in smaller chunks first
5. Include error handling - Add try/except blocks to capture issues gracefully

Alternative: Inline Python Command

For simple one-liners or short scripts:

python3 -c "import reportlab; print(reportlab.__version__)"

Troubleshooting

If shell execution also fails:

• Check if Python3 is available: which python3
• Verify package installation: pip3 list | grep package_name
• Try python instead of python3 (some systems differ)
• Consider installing the package: pip3 install package_name