Get block that's closest to timestamp with web3.py (Ethereum)

closest_block.py

from datetime import datetime

from web3 import Web3
from web3.types import BlockData
import logging


logger = logging.getLogger(__name__)


def get_closest_block(
    web3: Web3,
    wanted_datetime: datetime,
    *,
    not_before: bool = False
) -> BlockData:
    wanted_timestamp = int(wanted_datetime.timestamp())
    logger.debug("Wanted timestamp: %s", wanted_timestamp)
    start_block_number = 1
    end_block_number = web3.eth.block_number
    logger.debug("Bisecting between %s and %s", start_block_number, end_block_number)
    closest_block = None
    closest_diff = 2**256 - 1
    while start_block_number <= end_block_number:
        target_block_number = (start_block_number + end_block_number) // 2
        block: BlockData = web3.eth.get_block(target_block_number)
        block_timestamp = block['timestamp']

        diff = block_timestamp - wanted_timestamp
        logger.debug(
            "target: %s, timestamp: %s, diff %s",
            target_block_number,
            block_timestamp,
            diff
        )

        # Only update block when diff actually gets lower
        # This is only necessary in the last steps of the bisect, but we might as well do it every round
        if abs(diff) < closest_diff:
            closest_diff = abs(diff)
            closest_block = block

        if block_timestamp > wanted_timestamp:
            # block is after wanted, move end
            end_block_number = block['number'] - 1
        elif block_timestamp < wanted_timestamp:
            # block is before wanted, move start
            start_block_number = block['number'] + 1
        else:
            # timestamps are exactly the same, just return block
            return block

    if closest_block is None:
        raise LookupError('Unable to determine block closest to ' + wanted_datetime.isoformat())

    if not_before and closest_block["timestamp"] < wanted_timestamp:
        logger.debug("Block is before wanted timestamp and not_before=True, returning next block")
        return web3.eth.get_block(closest_block["number"] + 1)

    return closest_block