shell-python-heredoc

Shell Python Heredoc (Fallback Pattern)

Overview

When execute_code_sandbox fails repeatedly (e.g., with "unknown error"), use run_shell with a Python heredoc as a reliable fallback for executing multi-line Python scripts with imports.

When to Use

• execute_code_sandbox has failed 2+ times with unexplained errors
• You need to run Python code with multiple imports (e.g., ReportLab, pandas)
• The script is too complex for a one-liner but doesn't require persistence between calls
• You need better error visibility from raw stdout/stderr

How to Use

Basic Pattern

run_shell(
    command="""python3 << 'EOF'
import sys
# Your Python code here
print("Hello from heredoc")
EOF""",
    timeout=300
)

Key Syntax Rules

1. Use << 'EOF' (with single quotes) to prevent shell variable expansion
2. Indent Python code relative to the heredoc delimiter
3. End with EOF on its own line (no leading whitespace)
4. Capture output from stdout/stderr for debugging

Example: Generating a PDF with ReportLab

run_shell(
    command="""python3 << 'EOF'
from reportlab.lib.pagesizes import letter
from reportlab.pdfgen import canvas

c = canvas.Canvas("output.pdf", pagesize=letter)
c.drawString(100, 750, "Hello PDF")
c.save()
print("PDF created successfully")
EOF""",
    timeout=300
)

Example: Multi-file Data Processing

run_shell(
    command="""python3 << 'EOF'
import pandas as pd
import json

# Load and process data
df = pd.read_csv("data.csv")
summary = df.describe()

# Output results
print(summary.to_string())
with open("summary.json", "w") as f:
    json.dump(summary.to_dict(), f)
print("Processing complete")
EOF""",
    timeout=300
)

Advantages Over execute_code_sandbox

• More reliable for complex imports (no sandbox isolation issues)
• Full stdout/stderr access for debugging
• Longer timeout flexibility (60s default vs 30s)
• Direct filesystem access without ARTIFACT_PATH indirection

Disadvantages

• No persistent state between calls (each heredoc is a fresh process)
• Verbose for simple one-liners
• Shell escaping may be needed for complex string literals

Troubleshooting

Issue	Solution
EOF not recognized	Ensure EOF is on its own line with no leading spaces
Import errors	Verify packages are installed in the shell environment
File not found	Use absolute paths or check working directory with pwd
Syntax errors	Check Python indentation within heredoc

See Also

• Use execute_code_sandbox for simpler scripts when available
• Use shell_agent for tasks requiring autonomous iteration and error recovery
• Consider writing scripts to .py files for complex, reusable code