44. Working with Chainlink oracles in Vyper

Since contracts can't access the internet directly, price feeds and other external data come through oracles like Chainlink. You declare a small interface for the feed and call its `latestRoundData` (or similar) function.

interface AggregatorV3:
    def latestAnswer() -> int256: view

price_feed: public(address)

@external
@view
def get_price() -> int256:
    return AggregatorV3(self.price_feed).latestAnswer()

Always sanity-check oracle data (non-zero, not obviously stale) before using it for anything that moves funds, and consider what happens if the feed reverts or returns unexpected values.

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