How to parse JSON in Python: A Beginner's Guide with Code Examples

import json
from typing import Any, Dict, List, Optional


class DataHelper:
    """Beginner-friendly helper for common AI/LLM data tasks."""
    
    def __init__(self, data: Optional[Dict[str, Any]] = None):
        self.data = data or {}
    
    def to_prompt(self, template: str) -> str:
        """Format a prompt template using stored data."""
        try:
            return template.format(**self.data)
        except KeyError as e:
            raise ValueError(f"Missing key in data: {e}")
    
    def extract_fields(self, fields: List[str]) -> Dict[str, Any]:
        """Safely extract specific fields from nested data."""
        return {field: self._get_nested(field.split(".")) for field in fields}
    
    def _get_nested(self, path: List[str]) -> Any:
        current = self.data
        for key in path:
            if isinstance(current, dict) and key in current:
                current = current[key]
            else:
                return None
        return current
    
    def to_json(self) -> str:
        """Serialize data to JSON string."""
        return json.dumps(self.data, indent=2)


if __name__ == "__main__":
    sample = {
        "user": {"name": "Alice", "age": 30},
        "context": "coding help"
    }
    helper = DataHelper(sample)
    
    prompt = helper.to_prompt("Help {user[name]} with {context}.")
    extracted = helper.extract_fields(["user.name", "context", "user.age"])
    
    print(json.dumps({"prompt": prompt, "extracted": extracted}, indent=2))