What You’ll Learn
- Sending prompts to the Anthropic Messages API (
claude-sonnet-4-20250514) to generate executable Python code
- Stripping markdown code fences from LLM responses before execution
- Writing generated code into a Declaw sandbox filesystem
- Executing the code securely with
sbx.commands.run()
- Graceful demo mode when no API key is configured
Prerequisites
- Declaw instance running and
DECLAW_API_KEY / DECLAW_DOMAIN set
ANTHROPIC_API_KEY (optional — the example runs in demo mode without it)
pip install declaw python-dotenv anthropic
npm install @declaw/sdk dotenv @anthropic-ai/sdk
Code Walkthrough
1. Ask Claude to generate Python code
The Anthropic SDK uses client.messages.create(). The instruction to return only code is embedded in the user message:import anthropic
from declaw import Sandbox
client = anthropic.Anthropic()
response = client.messages.create(
model="claude-sonnet-4-20250514",
max_tokens=1024,
messages=[
{
"role": "user",
"content": (
"You are a Python code interpreter. When asked a question, "
"respond ONLY with Python code that computes the answer and "
"prints it. No markdown, no explanation, just code.\n\n"
"Question: What are the first 15 Fibonacci numbers?"
),
},
],
)
2. Strip code fences and execute in a sandbox
def strip_code_fences(code: str) -> str:
code = code.strip()
if code.startswith("```"):
code = "\n".join(code.split("\n")[1:])
if code.endswith("```"):
code = "\n".join(code.split("\n")[:-1])
return code.strip()
raw_text = response.content[0].text
code = strip_code_fences(raw_text)
sbx = Sandbox.create(template="python", timeout=300)
try:
sbx.files.write("/tmp/solution.py", code)
result = sbx.commands.run("python3 /tmp/solution.py", timeout=30)
print(result.stdout)
print(result.exit_code)
finally:
sbx.kill()
3. Demo mode (no API key needed)
code = """\
def fibonacci(n):
a, b = 0, 1
result = []
for _ in range(n):
result.append(a)
a, b = b, a + b
return result
print("First 15 Fibonacci numbers:", fibonacci(15))
print("Sum of first 100 integers:", sum(range(1, 101)))
"""
sbx = Sandbox.create(template="python", timeout=300)
try:
sbx.files.write("/tmp/demo.py", code)
result = sbx.commands.run("python3 /tmp/demo.py", timeout=30)
print(result.stdout)
finally:
sbx.kill()
1. Ask Claude to generate Python code
import { Sandbox } from "@declaw/sdk";
import Anthropic from "@anthropic-ai/sdk";
const client = new Anthropic();
const response = await client.messages.create({
model: "claude-sonnet-4-20250514",
max_tokens: 1024,
messages: [
{
role: "user",
content:
"You are a Python code interpreter. When asked a question, respond ONLY with Python code that computes the answer and prints it. No markdown, no explanation, just code.\n\nQuestion: What are the first 15 Fibonacci numbers?",
},
],
});
2. Strip code fences and execute in a sandbox
function stripCodeFences(code: string): string {
let cleaned = code.trim();
if (cleaned.startsWith("```")) {
cleaned = cleaned.split("\n").slice(1).join("\n");
}
if (cleaned.endsWith("```")) {
cleaned = cleaned.split("\n").slice(0, -1).join("\n");
}
return cleaned.trim();
}
const rawText =
response.content[0].type === "text" ? response.content[0].text : "";
const code = stripCodeFences(rawText);
const sbx = await Sandbox.create({ template: "python", timeout: 300 });
try {
await sbx.files.write("/tmp/solution.py", code);
const result = await sbx.commands.run("python3 /tmp/solution.py", {
timeout: 30,
});
console.log(result.stdout);
console.log(result.exitCode);
} finally {
await sbx.kill();
}
3. Demo mode (no API key needed)
const code = `
def fibonacci(n):
a, b = 0, 1
result = []
for _ in range(n):
result.append(a)
a, b = b, a + b
return result
print("First 15 Fibonacci numbers:", fibonacci(15))
print("Sum of first 100 integers:", sum(range(1, 101)))
`.trim();
const sbx = await Sandbox.create({ template: "python", timeout: 300 });
try {
await sbx.files.write("/tmp/demo.py", code);
const result = await sbx.commands.run("python3 /tmp/demo.py", { timeout: 30 });
console.log(result.stdout);
} finally {
await sbx.kill();
}
Expected Output
============================================================
Anthropic Code Interpreter with Declaw Sandbox
============================================================
--- Question: What are the first 15 Fibonacci numbers? ---
Generated code:
def fibonacci(n): ...
Result:
stdout: First 15 Fibonacci numbers: [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377]
stderr:
exit_code: 0
============================================================
Done!
============================================================
In demo mode (no ANTHROPIC_API_KEY), the output shows pre-written code results: the first 15 Fibonacci numbers and the sum of integers 1–100 (5050).
