How to Merge Multiple Data Sources in Python

import json

def merge_pipeline_data(*data_sources, keys=()):
    """Merge multiple data sources (list of dicts) into a single list of merged dicts.
    
    Args:
        *data_sources: One or more lists of dictionaries.
        keys: Tuple of keys to include from each source (empty means all keys).
    Returns:
        Merged list of dictionaries.
    """
    merged = []
    for idx, source in enumerate(data_sources):
        for record in source:
            filtered_record = {k: v for k, v in record.items() if k in keys} if keys else record
            if len(merged) <= idx:
                merged.append({})
            merged[idx].update(filtered_record)
    return merged

if __name__ == "__main__":
    users = [
        {"id": 1, "name": "Alice", "email": "alice@example.com"},
        {"id": 2, "name": "Bob", "email": "bob@example.com"}
    ]
    orders = [
        {"id": 1, "product": "Laptop", "cost": 1200},
        {"id": 2, "product": "Keyboard", "cost": 75}
    ]
    result = merge_pipeline_data(users, orders, keys=("id", "name", "product", "cost"))
    print(json.dumps(result, indent=2))