JSON Mode Prompt Schema Output in Python

Extract a user object to JSON with explicit schema keys, ready for LLM JSON-mode prompts.

Easy Python 3.9+ Aug 9, 2026 AI & LLM integration patterns 13 views 0 copies

json schema llm prompting extraction

Python code

20 lines

Python 3.9+

import json
from typing import Any, Dict


def extract_user_as_json(user: Dict[str, Any]) -> str:
    """Extract a user object and return it as JSON using explicit schema keys."""
    schema_fields = ("id", "name", "email", "is_active")
    user_subset = {key: user[key] for key in schema_fields if key in user}
    return json.dumps(user_subset, indent=2)


if __name__ == "__main__":
    sample_user = {
        "id": 42,
        "name": "Alice Johnson",
        "email": "alice@example.com",
        "is_active": True,
        "unused_field": "ignored",
    }
    print(extract_user_as_json(sample_user))

Output

stdout

{
  "id": 42,
  "name": "Alice Johnson",
  "email": "alice@example.com",
  "is_active": true
}

How it works

This function filters a user dict against a fixed tuple of schema fields, ignoring extras like unused_field, producing a clean JSON subset. json.dumps with indent=2 formats the output for readability in logs or LLM prompts. Using a tuple for schema_fields keeps the allowed keys explicit and immutable, which makes the contract easy to audit. The function returns a string, which is the standard input format for JSON-mode prompts on LLM APIs.

Common mistakes

Assuming all keys exist without checking `if key in user`
Including extra fields that break strict JSON schemas
Returning a dict instead of a JSON string for API calls

Variations

Add type validation with pydantic for stricter schema enforcement
Use `json.dumps(..., sort_keys=True)` for deterministic ordering

Real-world use cases

Preparing structured user data for LLM JSON-mode completions in chat assistants.
Filtering database records to match an API's expected response schema.
Sanitizing webhook payloads before sending them to an AI summarization service.

JSON Mode Prompt Schema Output in Python

Python code

Output

How it works

Common mistakes

Variations

Real-world use cases

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Python code

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Variations

Real-world use cases

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