from typing import Dict, Any, List


class Aggregator:
    def __init__(self):
        self._latest: Dict[str, float] = {}
        self._venues: List[str] = []

    def add_signal(self, venue: str, signal: str, value: float) -> None:
        key = f"{venue}:{signal}"
        self._latest[key] = value
        if venue not in self._venues:
            self._venues.append(venue)

    def aggregate_price(self) -> float:
        # Simple average across known venues for signal 'price'
        values = [v for k, v in self._latest.items() if k.endswith(":price")]
        if not values:
            return 0.0
        return sum(values) / len(values)