excel-heredoc-fallback

Excel Creation via Shell Heredoc Fallback

Overview

When creating Excel files with openpyxl, execute_code_sandbox may fail due to sandbox restrictions, missing dependencies, or permission issues. This skill provides a reliable fallback: execute Python code via run_shell using an inline heredoc script. This approach often succeeds where the sandbox fails and supports full openpyxl features including styling, formulas, and formatting.

When to Use This Skill

• execute_code_sandbox fails when importing or using openpyxl
• Sandbox shows errors about missing packages, permissions, or execution restrictions
• You need to create Excel files with advanced formatting (styles, colors, merged cells, formulas)
• Previous sandbox attempts have failed multiple times

Step-by-Step Instructions

Step 1: Attempt Sandbox Execution First

Always try execute_code_sandbox first, as it's cleaner and preferred when it works:

from openpyxl import Workbook
from openpyxl.styles import Font, Fill, PatternFill, Alignment

wb = Workbook()
ws = wb.active
ws['A1'] = 'Header'
ws['A1'].font = Font(bold=True)
wb.save('output.xlsx')

Step 2: Detect Sandbox Failure

Watch for these failure indicators:

• ImportError for openpyxl or related modules
• Permission denied errors
• File write failures
• Repeated retry loops without success
• Timeout or resource errors

Step 3: Fall Back to Shell Heredoc

When sandbox fails, switch to run_shell with a Python heredoc:

python3 << 'EOF'
from openpyxl import Workbook
from openpyxl.styles import Font, Fill, PatternFill, Alignment, Border, Side

# Create workbook
wb = Workbook()
ws = wb.active
ws.title = "Sheet1"

# Add data with formatting
ws['A1'] = 'Name'
ws['B1'] = 'Value'
ws['A1'].font = Font(bold=True, size=14)
ws['B1'].font = Font(bold=True, size=14)

# Add rows
data = [
    ['Item 1', 100],
    ['Item 2', 200],
    ['Item 3', 150],
]

for row_idx, row_data in enumerate(data, start=2):
    for col_idx, value in enumerate(row_data, start=1):
        cell = ws.cell(row=row_idx, column=col_idx, value=value)
        cell.alignment = Alignment(horizontal='center')

# Add formulas if needed
ws['B5'] = '=SUM(B2:B4)'

# Save the file
wb.save('output.xlsx')
print("Excel file created successfully: output.xlsx")
EOF

Step 4: Use run_shell Tool

Execute the heredoc via run_shell:

tool: run_shell
command: python3 << 'EOF'
[from openpyxl code here]
EOF

Step 5: Verify File Creation

After execution, confirm the file was created:

tool: run_shell
command: ls -lh output.xlsx

Check the file size to ensure it's not empty (should be >1KB for typical spreadsheets).

Best Practices

1. Use Single-Quoted Heredoc Delimiter

Always use << 'EOF' (with quotes) to prevent shell variable expansion inside the Python code.

2. Include Error Handling

Add try/except blocks to catch and report issues:

try:
    from openpyxl import Workbook
    # ... your code ...
    wb.save('output.xlsx')
    print("SUCCESS: File created")
except Exception as e:
    print(f"ERROR: {e}")
    exit(1)

3. Print Confirmation Messages

Always include print statements that confirm success or report specific errors. This helps debug issues.

4. Use Absolute or Explicit Paths

When saving files, use explicit paths to avoid confusion:

wb.save('./output.xlsx')  # Explicit current directory
# or
wb.save('/workspace/output.xlsx')  # Absolute path

5. Keep Scripts Concise

Heredoc scripts should be focused and not excessively long. If the Excel logic is complex, consider writing a separate .py file first using write_file, then executing it.

Advanced Formatting Examples

Cell Styling

from openpyxl.styles import Font, PatternFill, Alignment, Border, Side

# Define styles
bold_font = Font(bold=True, size=12)
header_fill = PatternFill(start_color='4472C4', end_color='4472C4', fill_type='solid')
center_align = Alignment(horizontal='center', vertical='center')
thin_border = Border(
    left=Side(style='thin'),
    right=Side(style='thin'),
    top=Side(style='thin'),
    bottom=Side(style='thin')
)

# Apply to cells
ws['A1'].font = bold_font
ws['A1'].fill = header_fill
ws['A1'].alignment = center_align

Column Width and Row Height

ws.column_dimensions['A'].width = 20
ws.column_dimensions['B'].width = 15
ws.row_dimensions[1].height = 25

Merged Cells

ws.merge_cells('A1:C1')
ws['A1'] = 'Merged Header'
ws['A1'].alignment = Alignment(horizontal='center')

Multiple Sheets

wb.create_sheet(title='Summary')
wb.create_sheet(title='Details')
ws_summary = wb['Summary']
ws_details = wb['Details']

Troubleshooting

| Issue | Solution | |-------|----------| | openpyxl not found | Add pip install openpyxl before Python script | | File not created | Check working directory, use absolute paths | | Permission denied | Ensure write permissions in target directory | | Encoding issues | Python 3 handles UTF-8 by default; specify if needed | | Large files time out | Increase run_shell timeout parameter |

Comparison: Sandbox vs. Shell Heredoc

| Aspect | execute_code_sandbox | run_shell heredoc | |--------|---------------------|-------------------| | Preferred | Yes (cleaner) | No (fallback) | | Dependencies | May be restricted | Uses system Python | | File access | Sandboxed | Full filesystem | | Styling support | Sometimes limited | Full support | | Debugging | Logs in tool output | Full stdout/stderr |

Example Complete Workflow

# Step 1: Try sandbox
tool: execute_code_sandbox
code: |
  from openpyxl import Workbook
  wb = Workbook()
  ws = wb.active
  ws['A1'] = 'Test'
  wb.save('test.xlsx')

# Step 2: If that fails, use shell heredoc
tool: run_shell
command: |
  python3 << 'EOF'
  from openpyxl import Workbook
  from openpyxl.styles import Font, PatternFill
  
  wb = Workbook()
  ws = wb.active
  
  ws['A1'] = 'Header'
  ws['A1'].font = Font(bold=True)
  ws['A1'].fill = PatternFill(start_color='FFFF00', fill_type='solid')
  
  wb.save('test.xlsx')
  print("Created: test.xlsx")
  EOF

# Step 3: Verify
tool: run_shell
command: ls -lh test.xlsx