I'm trying to execute my first contract on Ethereum. I've been able to compile and deploy one of Vyper's test examples of an auction. I believe the contract is executed when a transaction is sent to it. The thing I'm not yet understanding is when the constructor and the methods are called. As I understand it the bytecode is sent to the nodes for computation, but I'm missing how/when/where the constructor and the methods themselves are called. For instance, below I have a method called 'bid', but how does the transaction know how to call 'bid'? I think I'm not quite understanding the entire process from transaction submission down to contract execution. Thanks for your help!

beneficiary: public(address)
auctionStart: public(timestamp)
auctionEnd: public(timestamp)
highestBidder: public(address)
highestBid: public(uint256)
ended: public(bool)
pendingReturns: public(map(address, uint256))

def __init__(_beneficiary: address, _bidding_time: uint256):
    self.beneficiary = _beneficiary
    self.auctionStart = block.timestamp
    self.auctionEnd = self.auctionStart + _bidding_time

def bid():
    assert block.timestamp < self.auctionEnd
    assert msg.value > self.highestBid
    self.pendingReturns[self.highestBidder] += self.highestBid
    self.highestBidder = msg.sender
    self.highestBid = as_unitless_number(msg.value)

1 Answer 1


Each function has a signature. Inside of a transaction, there is a data field.

This data field contains what function signature you would like to call along with what arguments - Vyper compiles to EVM bytecode. This bytecode contains the function signatures.

  • Thank you Dylan. I was just starting out when I was working with this example. I didn't realize that the code was transactional in that I had to actually put the function on the ledger and then launch a transaction to get it to execute. I was having difficulty thinking in a distributed sense, but your note about the EVM bytecode is helpful as it gets distributed to many participants on the ledger and eventually executed sand verified.
    – jkovba
    Oct 22, 2020 at 22:06
  • Ok, im just reading through all of the old vyper questions on here :) - i didnt realise how few people where using the language until i saw how few questions there were :0. Oct 22, 2020 at 22:08

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